refactor(metadata): move cover resolution to extensions

lib/services/batch_metadata_re_enrich.dart

@@ -81,7 +81,6 @@ Map<String, dynamic> buildBatchReEnrichRequest({
   final request = <String, dynamic>{
     'file_path': item.filePath,
     'cover_url': '',
-    'max_quality': true,
     'embed_lyrics': settings.embedLyrics,
     'lyrics_mode': settings.lyricsMode,
     'artist_tag_mode': settings.artistTagMode,

lib/services/cover_download_service.dart

@@ -37,7 +37,6 @@ class CoverDownloadService {
       final download = await PlatformBridge.downloadCoverToFile(
         normalizedUrl,
         tempPath,
-        maxQuality: true,
       );
       final error = download['error']?.toString().trim() ?? '';
       if (error.isNotEmpty) throw StateError(error);

lib/services/download_request_payload.dart

@@ -18,7 +18,6 @@ class DownloadRequestPayload {
   final bool embedMetadata;
   final String artistTagMode;
   final bool embedLyrics;
-  final bool embedMaxQualityCover;
   final bool embedReplayGain;
   final bool postProcessingEnabled;
   final String tidalHighFormat;
@@ -80,7 +79,6 @@ class DownloadRequestPayload {
     this.embedMetadata = true,
     this.artistTagMode = 'joined',
     this.embedLyrics = true,
-    this.embedMaxQualityCover = true,
     this.embedReplayGain = false,
     this.postProcessingEnabled = false,
     this.tidalHighFormat = 'mp3_320',
@@ -144,7 +142,6 @@ class DownloadRequestPayload {
       'embed_metadata': embedMetadata,
       'artist_tag_mode': artistTagMode,
       'embed_lyrics': embedLyrics,
-      'embed_max_quality_cover': embedMaxQualityCover,
       'embed_replaygain': embedReplayGain,
       'post_processing_enabled': postProcessingEnabled,
       'tidal_high_format': tidalHighFormat,
@@ -212,7 +209,6 @@ class DownloadRequestPayload {
       embedMetadata: embedMetadata,
       artistTagMode: artistTagMode,
       embedLyrics: embedLyrics,
-      embedMaxQualityCover: embedMaxQualityCover,
       embedReplayGain: embedReplayGain,
       postProcessingEnabled: postProcessingEnabled,
       tidalHighFormat: tidalHighFormat,

lib/services/platform_bridge.dart

@@ -899,13 +899,11 @@ class PlatformBridge {
 
   static Future<Map<String, dynamic>> downloadCoverToFile(
     String coverUrl,
-    String outputPath, {
-    bool maxQuality = true,
-  }) {
+    String outputPath,
+  ) {
     return _invokeMap('downloadCoverToFile', {
       'cover_url': coverUrl,
       'output_path': outputPath,
-      'max_quality': maxQuality,
     });
   }