feat(library): add quality label display modes

lib/utils/audio_quality_badge_policy.dart

@@ -1,5 +1,44 @@
+import 'package:spotiflac_android/models/settings.dart';
+import 'package:spotiflac_android/utils/audio_format_utils.dart';
+import 'package:spotiflac_android/utils/string_utils.dart';
+
 const highQualityBadgeBitrateThresholdKbps = 900;
 
+String normalizeLibraryQualityLabelMode(String? mode) {
+  return mode == AppSettings.libraryQualityLabelBitDepth
+      ? AppSettings.libraryQualityLabelBitDepth
+      : AppSettings.libraryQualityLabelBitrate;
+}
+
+/// Builds a Library label from metadata already held in memory. Lossy formats
+/// keep their bitrate label because bit depth is not a useful quality signal
+/// for encoded MP3/AAC/Opus audio.
+String? buildLibraryAudioQualityLabel({
+  required String mode,
+  String? format,
+  int? bitrateKbps,
+  int? bitDepth,
+  int? sampleRate,
+  String? storedQuality,
+}) {
+  final bitrateLabel = bitrateKbps != null && bitrateKbps > 0
+      ? buildDisplayAudioQuality(bitrateKbps: bitrateKbps, format: format)
+      : null;
+  final bitDepthLabel =
+      bitDepth != null && bitDepth > 0 && sampleRate != null && sampleRate > 0
+      ? buildDisplayAudioQuality(bitDepth: bitDepth, sampleRate: sampleRate)
+      : null;
+  final fallback = normalizeOptionalString(storedQuality);
+
+  final useBitDepth =
+      normalizeLibraryQualityLabelMode(mode) ==
+          AppSettings.libraryQualityLabelBitDepth &&
+      !isLossyAudioFormat(format);
+  return useBitDepth
+      ? bitDepthLabel ?? bitrateLabel ?? fallback
+      : bitrateLabel ?? bitDepthLabel ?? fallback;
+}
+
 /// Preserves the highlighted color used by legacy 24-bit Library badges while
 /// also supporting newer labels that display a measured bitrate instead.
 bool shouldHighlightAudioQualityBadge(String quality) {