feat(metadata): add safe batch editing and matching

lib/services/batch_metadata_re_enrich.dart

@@ -20,13 +20,34 @@ class ReEnrichFields {
   ];
 }
 
-enum ReEnrichBatchMode { isrcOnly, missingOnly, selectedFields }
+enum ReEnrichBatchMode { isrcOnly, missingOnly, selectedFields, manualValues }
+
+/// Tags where applying one shared value to multiple tracks is normally safe.
+/// Per-track identifiers, titles, and track/disc numbers are deliberately
+/// excluded so the batch editor cannot accidentally duplicate them.
+const List<String> manualBatchMetadataFields = [
+  'artist_name',
+  'album_name',
+  'album_artist',
+  'release_date',
+  'genre',
+  'composer',
+  'label',
+  'copyright',
+];
 
 class ReEnrichFieldSelection {
   final ReEnrichBatchMode mode;
   final List<String> fields;
+  final Map<String, String> manualValues;
 
-  const ReEnrichFieldSelection({required this.mode, this.fields = const []});
+  const ReEnrichFieldSelection({
+    required this.mode,
+    this.fields = const [],
+    this.manualValues = const {},
+  });
+
+  bool get usesManualValues => mode == ReEnrichBatchMode.manualValues;
 
   List<String> updateFieldsFor(LocalLibraryItem item) {
     switch (mode) {
@@ -36,6 +57,15 @@ class ReEnrichFieldSelection {
         return fields;
       case ReEnrichBatchMode.missingOnly:
         return missingReEnrichFields(item);
+      case ReEnrichBatchMode.manualValues:
+        return manualValues.entries
+            .where(
+              (entry) =>
+                  manualBatchMetadataFields.contains(entry.key) &&
+                  entry.value.trim().isNotEmpty,
+            )
+            .map((entry) => entry.key)
+            .toList(growable: false);
     }
   }
 }
@@ -138,6 +168,36 @@ class BatchReEnrichPreview {
   });
 }
 
+BatchReEnrichPreview? buildManualBatchReEnrichPreview(
+  LocalLibraryItem item,
+  ReEnrichFieldSelection selection,
+) {
+  if (!selection.usesManualValues) return null;
+
+  final enrichedMetadata = <String, dynamic>{
+    for (final entry in selection.manualValues.entries)
+      if (manualBatchMetadataFields.contains(entry.key) &&
+          entry.value.trim().isNotEmpty)
+        entry.key: entry.value.trim(),
+  };
+  final updateFields = enrichedMetadata.keys.toList(growable: false);
+  if (updateFields.isEmpty) return null;
+
+  final changes = buildReEnrichMetadataChanges(
+    item,
+    enrichedMetadata,
+    updateFields,
+  );
+  if (changes.isEmpty) return null;
+
+  return BatchReEnrichPreview(
+    item: item,
+    updateFields: updateFields,
+    enrichedMetadata: enrichedMetadata,
+    changes: changes,
+  );
+}
+
 String _displayValue(Object? value) {
   if (value == null) return '';
   if (value is num && value == 0) return '';

lib/services/library_database_queue_sql.dart

@@ -2,6 +2,11 @@ part of 'library_database.dart';
 
 // SQL builders for the queue tab's history+local union queries.
 
+String confirmedMissingLyricsSqlPredicate({
+  required String hasLyricsExpr,
+  required String lyricsKnownExpr,
+}) => '($lyricsKnownExpr) AND COALESCE($hasLyricsExpr, 0) = 0';
+
 class _QueueOrderTerm {
   final String column;
   final bool descending;
@@ -398,6 +403,7 @@ extension _LibraryDbQueueSql on LibraryDatabase {
       isrcExpr: 'h.isrc',
       labelExpr: 'h.label',
       hasLyricsExpr: 'h.has_lyrics',
+      lyricsKnownExpr: 'COALESCE(h.lyrics_metadata_scan_version, 0) >= 1',
     );
   }
 
@@ -441,6 +447,8 @@ extension _LibraryDbQueueSql on LibraryDatabase {
       isrcExpr: 'l.isrc',
       labelExpr: 'l.label',
       hasLyricsExpr: 'l.has_lyrics',
+      lyricsKnownExpr:
+          'COALESCE(l.audio_metadata_scan_version, 0) >= ${LibraryDatabase.audioMetadataScanVersion}',
     );
   }
 
@@ -461,6 +469,7 @@ extension _LibraryDbQueueSql on LibraryDatabase {
     required String isrcExpr,
     required String labelExpr,
     required String hasLyricsExpr,
+    required String lyricsKnownExpr,
   }) {
     final quality = request.quality?.trim().toLowerCase();
     if (quality != null && quality.isNotEmpty) {
@@ -546,7 +555,14 @@ extension _LibraryDbQueueSql on LibraryDatabase {
         where.add('NOT ($hasLabel)');
         break;
       case 'missing-lyrics':
-        where.add('COALESCE($hasLyricsExpr, 0) = 0');
+        // A default false value on legacy rows means "not scanned yet", not
+        // "confirmed missing". Only show files whose lyrics probe completed.
+        where.add(
+          confirmedMissingLyricsSqlPredicate(
+            hasLyricsExpr: hasLyricsExpr,
+            lyricsKnownExpr: lyricsKnownExpr,
+          ),
+        );
         break;
     }
   }