refactor(layering): move logic files out of screens

Search bucketing, refresh policy, folder data, history snapshot and the
selection and collapsing-header mixins hold no widgets, so they move to
controllers; the settings search catalog is pure presentation metadata and
moves to utils. Files with many importers keep a re-export in screens.

lib/controllers/collapsing_header_scroll_mixin.dart

@@ -0,0 +1,41 @@
+import 'package:flutter/material.dart';
+
+/// Expanded height of the album-style collapsing header, shared with the
+/// loading screens that show the same header before the tracks arrive.
+double collectionHeaderExpandedHeight(BuildContext context) {
+  final mediaSize = MediaQuery.sizeOf(context);
+  return (mediaSize.height * 0.6).clamp(400.0, 580.0);
+}
+
+/// Shared collapsing-header scroll behavior for album-style screens: owns the
+/// [ScrollController] and flips [showTitleInAppBar] once the header has
+/// scrolled out of view.
+mixin CollapsingHeaderScrollMixin<T extends StatefulWidget> on State<T> {
+  final ScrollController scrollController = ScrollController();
+  bool showTitleInAppBar = false;
+
+  @override
+  void initState() {
+    super.initState();
+    scrollController.addListener(_onHeaderScroll);
+  }
+
+  @override
+  void dispose() {
+    scrollController.removeListener(_onHeaderScroll);
+    scrollController.dispose();
+    super.dispose();
+  }
+
+  double calculateExpandedHeight(BuildContext context) =>
+      collectionHeaderExpandedHeight(context);
+
+  void _onHeaderScroll() {
+    final expandedHeight = calculateExpandedHeight(context);
+    final shouldShow =
+        scrollController.offset > (expandedHeight - kToolbarHeight - 20);
+    if (shouldShow != showTitleInAppBar) {
+      setState(() => showTitleInAppBar = shouldShow);
+    }
+  }
+}

lib/controllers/library_tracks_folder_data.dart

@@ -1,5 +1,5 @@
 import 'package:spotiflac_android/models/track.dart';
-import 'package:spotiflac_android/screens/track_history_snapshot.dart';
+import 'package:spotiflac_android/controllers/track_history_snapshot.dart';
 import 'package:spotiflac_android/providers/library_collections_provider.dart';
 import 'package:spotiflac_android/services/history_database.dart';
 

lib/controllers/selection_mode_mixin.dart

@@ -0,0 +1,56 @@
+import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
+
+/// Shared multi-select state for list screens: enter/exit selection mode,
+/// toggle individual items, select all, and prune ids that fell out of the
+/// current item list. Mix into a `State<T>` alongside the screen's own
+/// per-item lookups (e.g. queue_tab, library_folder, artist screens).
+mixin SelectionModeMixin<T extends StatefulWidget> on State<T> {
+  bool isSelectionMode = false;
+  final Set<String> selectedIds = {};
+
+  void enterSelectionMode(String itemId) {
+    HapticFeedback.mediumImpact();
+    setState(() {
+      isSelectionMode = true;
+      selectedIds.add(itemId);
+    });
+  }
+
+  void exitSelectionMode() {
+    setState(() {
+      isSelectionMode = false;
+      selectedIds.clear();
+    });
+  }
+
+  void toggleSelection(String itemId) {
+    setState(() {
+      if (selectedIds.contains(itemId)) {
+        selectedIds.remove(itemId);
+        if (selectedIds.isEmpty) {
+          isSelectionMode = false;
+        }
+      } else {
+        selectedIds.add(itemId);
+      }
+    });
+  }
+
+  void selectAll(Iterable<String> ids) {
+    setState(() {
+      selectedIds.addAll(ids);
+    });
+  }
+
+  /// Drops ids no longer present in [validIds]; call from build() with the
+  /// current item ids. Exits selection mode next frame if that empties it.
+  void pruneSelection(Set<String> validIds) {
+    selectedIds.removeWhere((id) => !validIds.contains(id));
+    if (selectedIds.isEmpty && isSelectionMode) {
+      WidgetsBinding.instance.addPostFrameCallback((_) {
+        if (mounted) setState(() => isSelectionMode = false);
+      });
+    }
+  }
+}

lib/controllers/track_history_snapshot.dart

@@ -0,0 +1,20 @@
+import 'package:spotiflac_android/models/track.dart';
+import 'package:spotiflac_android/providers/download_history_provider.dart';
+import 'package:spotiflac_android/services/history_database.dart';
+
+/// Retains derived lookups while the immutable source list is unchanged.
+/// Callers replace their list for metadata, order, or filter changes.
+class TrackHistorySnapshot {
+  List<Track>? _source;
+  HistoryBatchLookupRequest request = HistoryBatchLookupRequest.snapshot([]);
+
+  List<HistoryLookupRequest> get lookups => request.tracks;
+
+  void update(List<Track> tracks) {
+    if (identical(tracks, _source)) return;
+    _source = tracks;
+    request = HistoryBatchLookupRequest.snapshot(
+      tracks.map(historyLookupForTrack),
+    );
+  }
+}

lib/screens/collapsing_header_scroll_mixin.dart

@@ -1,41 +1 @@
-import 'package:flutter/material.dart';
-
-/// Expanded height of the album-style collapsing header, shared with the
-/// loading screens that show the same header before the tracks arrive.
-double collectionHeaderExpandedHeight(BuildContext context) {
-  final mediaSize = MediaQuery.sizeOf(context);
-  return (mediaSize.height * 0.6).clamp(400.0, 580.0);
-}
-
-/// Shared collapsing-header scroll behavior for album-style screens: owns the
-/// [ScrollController] and flips [showTitleInAppBar] once the header has
-/// scrolled out of view.
-mixin CollapsingHeaderScrollMixin<T extends StatefulWidget> on State<T> {
-  final ScrollController scrollController = ScrollController();
-  bool showTitleInAppBar = false;
-
-  @override
-  void initState() {
-    super.initState();
-    scrollController.addListener(_onHeaderScroll);
-  }
-
-  @override
-  void dispose() {
-    scrollController.removeListener(_onHeaderScroll);
-    scrollController.dispose();
-    super.dispose();
-  }
-
-  double calculateExpandedHeight(BuildContext context) =>
-      collectionHeaderExpandedHeight(context);
-
-  void _onHeaderScroll() {
-    final expandedHeight = calculateExpandedHeight(context);
-    final shouldShow =
-        scrollController.offset > (expandedHeight - kToolbarHeight - 20);
-    if (shouldShow != showTitleInAppBar) {
-      setState(() => showTitleInAppBar = shouldShow);
-    }
-  }
-}
+export 'package:spotiflac_android/controllers/collapsing_header_scroll_mixin.dart';

lib/screens/home_tab.dart

@@ -54,7 +54,7 @@ import 'package:spotiflac_android/screens/track_metadata_screen.dart';
 import 'package:spotiflac_android/screens/album_screen.dart';
 import 'package:spotiflac_android/screens/artist_screen.dart';
 import 'package:spotiflac_android/screens/extension_collection_screens.dart';
-import 'package:spotiflac_android/screens/home_search_logic.dart';
+import 'package:spotiflac_android/controllers/home_search_logic.dart';
 import 'package:spotiflac_android/services/csv_import_service.dart';
 import 'package:spotiflac_android/services/cover_download_service.dart';
 import 'package:spotiflac_android/services/downloaded_embedded_cover_resolver.dart';

lib/screens/library_tracks_folder_screen.dart

@@ -35,7 +35,7 @@ import 'package:spotiflac_android/utils/adaptive_layout.dart';
 import 'package:spotiflac_android/utils/cover_art_utils.dart';
 import 'package:spotiflac_android/screens/collapsing_header_scroll_mixin.dart';
 import 'package:spotiflac_android/screens/selection_mode_mixin.dart';
-import 'package:spotiflac_android/screens/library_tracks_folder_data.dart';
+import 'package:spotiflac_android/controllers/library_tracks_folder_data.dart';
 import 'package:spotiflac_android/screens/track_metadata_screen.dart';
 import 'package:spotiflac_android/widgets/selection_action_button.dart';
 import 'package:spotiflac_android/widgets/selection_bottom_bar.dart';

lib/screens/queue_tab.dart

@@ -80,7 +80,7 @@ import 'package:spotiflac_android/services/cover_cache_manager.dart';
 import 'package:spotiflac_android/screens/library_tracks_folder_screen.dart';
 import 'package:spotiflac_android/screens/local_album_screen.dart';
 import 'package:spotiflac_android/screens/mornye_library_screen.dart';
-import 'package:spotiflac_android/screens/queue_library_refresh_policy.dart';
+import 'package:spotiflac_android/controllers/queue_library_refresh_policy.dart';
 import 'package:spotiflac_android/utils/clickable_metadata.dart';
 import 'package:spotiflac_android/utils/string_utils.dart';
 import 'package:spotiflac_android/widgets/download_service_picker.dart';

lib/screens/selection_mode_mixin.dart

@@ -1,56 +1 @@
-import 'package:flutter/material.dart';
-import 'package:flutter/services.dart';
-
-/// Shared multi-select state for list screens: enter/exit selection mode,
-/// toggle individual items, select all, and prune ids that fell out of the
-/// current item list. Mix into a `State<T>` alongside the screen's own
-/// per-item lookups (e.g. queue_tab, library_folder, artist screens).
-mixin SelectionModeMixin<T extends StatefulWidget> on State<T> {
-  bool isSelectionMode = false;
-  final Set<String> selectedIds = {};
-
-  void enterSelectionMode(String itemId) {
-    HapticFeedback.mediumImpact();
-    setState(() {
-      isSelectionMode = true;
-      selectedIds.add(itemId);
-    });
-  }
-
-  void exitSelectionMode() {
-    setState(() {
-      isSelectionMode = false;
-      selectedIds.clear();
-    });
-  }
-
-  void toggleSelection(String itemId) {
-    setState(() {
-      if (selectedIds.contains(itemId)) {
-        selectedIds.remove(itemId);
-        if (selectedIds.isEmpty) {
-          isSelectionMode = false;
-        }
-      } else {
-        selectedIds.add(itemId);
-      }
-    });
-  }
-
-  void selectAll(Iterable<String> ids) {
-    setState(() {
-      selectedIds.addAll(ids);
-    });
-  }
-
-  /// Drops ids no longer present in [validIds]; call from build() with the
-  /// current item ids. Exits selection mode next frame if that empties it.
-  void pruneSelection(Set<String> validIds) {
-    selectedIds.removeWhere((id) => !validIds.contains(id));
-    if (selectedIds.isEmpty && isSelectionMode) {
-      WidgetsBinding.instance.addPostFrameCallback((_) {
-        if (mounted) setState(() => isSelectionMode = false);
-      });
-    }
-  }
-}
+export 'package:spotiflac_android/controllers/selection_mode_mixin.dart';

lib/screens/settings/settings_tab.dart

@@ -23,7 +23,7 @@ import 'package:spotiflac_android/screens/settings/log_screen.dart';
 import 'package:spotiflac_android/screens/settings/lyrics_settings_page.dart';
 import 'package:spotiflac_android/screens/settings/metadata_settings_page.dart';
 import 'package:spotiflac_android/screens/settings/playback_settings_page.dart';
-import 'package:spotiflac_android/screens/settings/settings_search_catalog.dart';
+import 'package:spotiflac_android/utils/settings_search_catalog.dart';
 import 'package:spotiflac_android/services/app_remote_config_service.dart';
 import 'package:spotiflac_android/theme/app_tokens.dart';
 import 'package:spotiflac_android/theme/mornye_theme.dart';

lib/screens/track_history_snapshot.dart

@@ -1,20 +1 @@
-import 'package:spotiflac_android/models/track.dart';
-import 'package:spotiflac_android/providers/download_history_provider.dart';
-import 'package:spotiflac_android/services/history_database.dart';
-
-/// Retains derived lookups while the immutable source list is unchanged.
-/// Callers replace their list for metadata, order, or filter changes.
-class TrackHistorySnapshot {
-  List<Track>? _source;
-  HistoryBatchLookupRequest request = HistoryBatchLookupRequest.snapshot([]);
-
-  List<HistoryLookupRequest> get lookups => request.tracks;
-
-  void update(List<Track> tracks) {
-    if (identical(tracks, _source)) return;
-    _source = tracks;
-    request = HistoryBatchLookupRequest.snapshot(
-      tracks.map(historyLookupForTrack),
-    );
-  }
-}
+export 'package:spotiflac_android/controllers/track_history_snapshot.dart';

test/autoplay_settings_test.dart

@@ -9,7 +9,7 @@ import 'package:spotiflac_android/models/settings.dart';
 import 'package:spotiflac_android/models/theme_settings.dart';
 import 'package:spotiflac_android/providers/settings_provider.dart';
 import 'package:spotiflac_android/screens/settings/playback_settings_page.dart';
-import 'package:spotiflac_android/screens/settings/settings_search_catalog.dart';
+import 'package:spotiflac_android/utils/settings_search_catalog.dart';
 import 'package:spotiflac_android/theme/app_theme.dart';
 import 'package:spotiflac_android/theme/mornye_theme.dart';
 import 'package:spotiflac_android/widgets/settings_group.dart';

test/library_tracks_folder_data_test.dart

@@ -1,7 +1,7 @@
 import 'dart:collection';
 import 'package:spotiflac_android/models/track.dart';
 import 'package:spotiflac_android/providers/library_collections_provider.dart';
-import 'package:spotiflac_android/screens/library_tracks_folder_data.dart';
+import 'package:spotiflac_android/controllers/library_tracks_folder_data.dart';
 import 'package:spotiflac_android/services/history_database.dart';
 import 'package:flutter_test/flutter_test.dart';
 

test/maintainability_contracts_test.dart

@@ -6,7 +6,7 @@ import 'package:spotiflac_android/models/download_item.dart';
 import 'package:spotiflac_android/models/track.dart';
 import 'package:spotiflac_android/providers/download_queue_state.dart';
 import 'package:spotiflac_android/providers/extension_provider.dart';
-import 'package:spotiflac_android/screens/home_search_logic.dart';
+import 'package:spotiflac_android/controllers/home_search_logic.dart';
 import 'package:spotiflac_android/services/audio_metadata_mapper.dart';
 import 'package:spotiflac_android/services/ffmpeg_models.dart';
 import 'package:spotiflac_android/services/id3v23_lyrics.dart';

test/playback_automation_settings_test.dart

@@ -9,7 +9,7 @@ import 'package:spotiflac_android/models/settings.dart';
 import 'package:spotiflac_android/models/theme_settings.dart';
 import 'package:spotiflac_android/providers/settings_provider.dart';
 import 'package:spotiflac_android/screens/settings/playback_settings_page.dart';
-import 'package:spotiflac_android/screens/settings/settings_search_catalog.dart';
+import 'package:spotiflac_android/utils/settings_search_catalog.dart';
 import 'package:spotiflac_android/theme/app_theme.dart';
 import 'package:spotiflac_android/theme/mornye_theme.dart';
 import 'package:spotiflac_android/widgets/settings_group.dart';

test/queue_library_refresh_policy_test.dart

@@ -3,7 +3,7 @@ import 'dart:io';
 import 'package:flutter_test/flutter_test.dart';
 
 import 'package:spotiflac_android/models/settings.dart';
-import 'package:spotiflac_android/screens/queue_library_refresh_policy.dart';
+import 'package:spotiflac_android/controllers/queue_library_refresh_policy.dart';
 import 'package:spotiflac_android/services/library_database.dart';
 
 void main() {