feat(ui): add Mornye glass theme and adaptive music player

Add a selectable Mornye theme with shared glass controls, dialogs, sheets, notifications, and collection headers while retaining Material components.

Update player artwork, lyrics transitions and highlighting, synchronized rolling time labels, volume controls, and compact navigation. Unify metadata, Library, search, and extension surfaces; preserve restored artwork and report extension load failures.

Validation: full Flutter analyzer clean; 713 tests passed and 4 skipped; pinned Dart formatting and diff checks passed; signed ARM64 and ARM32 release APKs built and verified.

lib/widgets/batch_convert_sheet.dart

@@ -1,11 +1,15 @@
 import 'package:flutter/material.dart';
+import 'package:flutter/cupertino.dart' show CupertinoIcons;
+import 'package:spotiflac_android/theme/mornye_theme.dart';
+import 'package:spotiflac_android/widgets/app_action_button.dart';
+import 'package:spotiflac_android/widgets/mornye_chrome.dart';
+import 'package:spotiflac_android/widgets/app_switch.dart';
 import 'package:spotiflac_android/widgets/app_bottom_sheet.dart';
 import 'package:spotiflac_android/l10n/l10n.dart';
 import 'package:spotiflac_android/utils/audio_conversion_utils.dart';
 import 'package:spotiflac_android/widgets/settings_group.dart';
 
-/// Modern, card-based batch convert sheet shared by the queue and album
-/// screens, matching the single-track convert sheet styling.
+/// Conversion options shared by the queue, album and single-track sheets.
 class BatchConvertSheet extends StatefulWidget {
   final List<String> formats;
   final String title;
@@ -93,7 +97,7 @@ class _BatchConvertSheetState extends State<BatchConvertSheet> {
         minChildSize: 0.5,
         maxChildSize: 0.95,
         expand: false,
-        builder: (context, scrollController) => SafeArea(
+        builder: (context, scrollController) => _sheetSurface(
           child: SingleChildScrollView(
             controller: scrollController,
             padding: const EdgeInsets.fromLTRB(20, 12, 20, 20),
@@ -327,13 +331,21 @@ class _BatchConvertSheetState extends State<BatchConvertSheet> {
                       horizontal: 14,
                       vertical: 12,
                     ),
-                    decoration: BoxDecoration(
-                      color: cs.primaryContainer.withValues(alpha: 0.4),
-                      borderRadius: BorderRadius.circular(14),
-                    ),
+                    decoration: context.isMornye
+                        ? null
+                        : BoxDecoration(
+                            color: cs.primaryContainer.withValues(alpha: 0.4),
+                            borderRadius: BorderRadius.circular(14),
+                          ),
                     child: Row(
                       children: [
-                        Icon(Icons.verified, size: 18, color: cs.primary),
+                        Icon(
+                          context.isMornye
+                              ? CupertinoIcons.checkmark_seal
+                              : Icons.verified,
+                          size: 18,
+                          color: cs.primary,
+                        ),
                         const SizedBox(width: 8),
                         Expanded(
                           child: Text(
@@ -364,7 +376,7 @@ class _BatchConvertSheetState extends State<BatchConvertSheet> {
 
                 _card(
                   cs,
-                  child: SwitchListTile(
+                  child: AppSwitchListTile(
                     contentPadding: EdgeInsets.zero,
                     title: Text(context.l10n.trackConvertKeepOriginal),
                     subtitle: Text(
@@ -378,7 +390,7 @@ class _BatchConvertSheetState extends State<BatchConvertSheet> {
                 const SizedBox(height: 8),
                 SizedBox(
                   width: double.infinity,
-                  child: FilledButton.icon(
+                  child: AppActionButton(
                     onPressed: () => widget.onConvert(
                       _selectedFormat,
                       _selectedBitrate,
@@ -421,7 +433,27 @@ class _BatchConvertSheetState extends State<BatchConvertSheet> {
     );
   }
 
+  Widget _sheetSurface({required Widget child}) {
+    final content = SafeArea(child: child);
+    return context.isMornye
+        ? MornyeGlassPanel.overlay(child: content)
+        : content;
+  }
+
   Widget _card(ColorScheme cs, {required Widget child}) {
+    if (context.isMornye) {
+      return Padding(
+        padding: const EdgeInsets.only(bottom: 20),
+        child: Column(
+          crossAxisAlignment: CrossAxisAlignment.stretch,
+          children: [
+            child,
+            const SizedBox(height: 20),
+            const Divider(height: 1),
+          ],
+        ),
+      );
+    }
     return Container(
       width: double.infinity,
       margin: const EdgeInsets.only(bottom: 12),
@@ -458,6 +490,15 @@ class _BatchConvertSheetState extends State<BatchConvertSheet> {
     required bool selected,
     required VoidCallback onTap,
   }) {
+    if (context.isMornye) {
+      return MornyeFilterChip(
+        label: label,
+        selected: selected,
+        onTap: onTap,
+        icon: selected ? CupertinoIcons.checkmark : null,
+        glass: false,
+      );
+    }
     return Material(
       color: selected ? cs.primaryContainer : cs.surface,
       borderRadius: BorderRadius.circular(14),