fix(ci): exclude bin/ from root analyzer and clean remaining warnings

The frontend CI job ran `flutter analyze` from the repo root, which also
analyzed the bin/ server package without its dependencies resolved
(shelf_router, sqlite3, bcrypt, test), producing hundreds of
uri_does_not_exist errors. bin/ is a standalone package covered by the
backend job, so it is now excluded from root analysis.

Also:
- Remove all unused fields/variables flagged as analyzer warnings
  (api_client, cache_service, player_screen, subtitle_service,
  live_tv_tab, mobile screens)
- Run `flutter analyze --no-fatal-infos` in CI: pre-existing deprecation
  infos (withOpacity, dart:html) stay non-fatal while errors and warnings
  still fail the build

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/core/services/cache_service.dart

@@ -28,7 +28,6 @@ class CacheEntry<T> {
 /// Optimized cache service for memory management
 class CacheService {
   static const _maxMemoryCacheSizeMb = 200;
-  static const _maxImageCacheItems = 500;
 
   final Map<String, CacheEntry> _cache = {};
   int _totalSizeBytes = 0;
@@ -83,7 +82,6 @@ class CacheService {
 
   /// Clear expired entries
   void clearExpired() {
-    final now = DateTime.now();
     final toRemove = _cache.entries
         .where((e) => e.value.isExpired())
         .map((e) => e.key)