refactor(providers): split download history out of download_queue_provider

download_queue_provider.dart (9,525 lines) hosted the entire download
history feature alongside the queue. Move DownloadHistoryItem/State/
Notifier and the history providers to download_history_provider.dart,
and promote the audio format/quality helpers both need into
lib/utils/audio_format_utils.dart. The queue provider re-exports the
history library, so existing imports keep working unchanged.

lib/utils/audio_format_utils.dart

@@ -0,0 +1,150 @@
+import 'package:spotiflac_android/utils/int_utils.dart';
+import 'package:spotiflac_android/utils/string_utils.dart';
+
+/// Audio format/quality helpers shared by the download queue and history
+/// providers.
+int? readPositiveBitrateKbps(dynamic value) {
+  final parsed = readPositiveInt(value);
+  if (parsed == null) return null;
+  final kbps = parsed >= 10000 ? (parsed / 1000).round() : parsed;
+  return kbps >= 16 ? kbps : null;
+}
+
+String? audioFormatForPath(String? filePath, {String? fileName}) {
+  final candidates = <String>[?filePath, ?fileName];
+  for (final candidate in candidates) {
+    final lower = candidate.trim().toLowerCase();
+    if (lower.endsWith('.opus') || lower.endsWith('.ogg')) return 'OPUS';
+    if (lower.endsWith('.mp3')) return 'MP3';
+    if (lower.endsWith('.aac')) return 'AAC';
+    if (lower.endsWith('.m4a') || lower.endsWith('.mp4')) return 'M4A';
+  }
+  return null;
+}
+
+String? nonPlaceholderQuality(String? quality) {
+  final normalized = normalizeOptionalString(quality);
+  if (normalized == null || isPlaceholderQualityLabel(normalized)) {
+    return null;
+  }
+  final bitrateMatch = RegExp(
+    r'\b(\d+)\s*kbps\b',
+    caseSensitive: false,
+  ).firstMatch(normalized);
+  if (bitrateMatch != null) {
+    final bitrate = int.tryParse(bitrateMatch.group(1) ?? '');
+    if (bitrate != null && bitrate < 16) return null;
+  }
+  final lower = normalized.toLowerCase().replaceAll(RegExp(r'[^a-z0-9]+'), '_');
+  const requestedLosslessLabels = {
+    'hi_res_lossless',
+    'hires_lossless',
+    'hi_res',
+    'hires',
+    'flac_best_available',
+  };
+  if (requestedLosslessLabels.contains(lower)) return null;
+  return normalized;
+}
+
+String? normalizeAudioFormatValue(String? value) {
+  final normalized = normalizeOptionalString(
+    value,
+  )?.toLowerCase().replaceAll('-', '_');
+  return switch (normalized) {
+    'flac' => 'flac',
+    'alac' => 'alac',
+    'aac' || 'mp4a' => 'aac',
+    'eac3' || 'ec_3' => 'eac3',
+    'ac3' || 'ac_3' => 'ac3',
+    'ac4' || 'ac_4' => 'ac4',
+    'mp3' => 'mp3',
+    'opus' || 'ogg' => 'opus',
+    'm4a' || 'mp4' => 'm4a',
+    _ => null,
+  };
+}
+
+bool isLossyAudioFormat(String? value) {
+  return const {
+    'aac',
+    'eac3',
+    'ac3',
+    'ac4',
+    'mp3',
+    'opus',
+    'm4a',
+  }.contains(normalizeAudioFormatValue(value));
+}
+
+String lossyFormatForSetting(String value) {
+  final normalized = value.trim().toLowerCase();
+  if (normalized.startsWith('opus')) return 'opus';
+  if (normalized.startsWith('aac') || normalized.startsWith('m4a')) {
+    return 'aac';
+  }
+  return 'mp3';
+}
+
+String lossyExtensionForFormat(String format) {
+  return switch (format) {
+    'opus' => '.opus',
+    'aac' => '.m4a',
+    _ => '.mp3',
+  };
+}
+
+String metadataFormatForLossyFormat(String format) {
+  return format == 'aac' ? 'm4a' : format;
+}
+
+String displayFormatForLossyFormat(String format) {
+  return format == 'aac' ? 'AAC' : format.toUpperCase();
+}
+
+String? resolveDisplayQuality({
+  required String? filePath,
+  String? fileName,
+  String? detectedFormat,
+  int? bitDepth,
+  int? sampleRate,
+  int? bitrateKbps,
+  String? storedQuality,
+}) {
+  final format =
+      displayFormatForCodec(detectedFormat) ??
+      audioFormatForPath(filePath, fileName: fileName);
+  if (format == 'OPUS' ||
+      format == 'MP3' ||
+      format == 'AAC' ||
+      format == 'EAC3' ||
+      format == 'AC3' ||
+      format == 'AC4' ||
+      (format == 'M4A' && (bitDepth == null || bitDepth <= 0))) {
+    return buildDisplayAudioQuality(bitrateKbps: bitrateKbps, format: format) ??
+        nonPlaceholderQuality(storedQuality) ??
+        format;
+  }
+  return buildDisplayAudioQuality(
+    bitDepth: bitDepth,
+    sampleRate: sampleRate,
+    storedQuality: nonPlaceholderQuality(storedQuality) ?? storedQuality,
+  );
+}
+
+String? displayFormatForCodec(String? value) {
+  final normalized = normalizeOptionalString(
+    value,
+  )?.toLowerCase().replaceAll('-', '_');
+  return switch (normalized) {
+    'flac' => 'FLAC',
+    'alac' => 'ALAC',
+    'aac' || 'mp4a' => 'AAC',
+    'eac3' || 'ec_3' => 'EAC3',
+    'ac3' || 'ac_3' => 'AC3',
+    'ac4' || 'ac_4' => 'AC4',
+    'mp3' => 'MP3',
+    'opus' => 'OPUS',
+    _ => null,
+  };
+}