feat: Complete watchlist & auto-download system with UI

Implement comprehensive watchlist system with automatic episode detection
and downloading. Features include per-user watchlists, scheduler-based
periodic checks, and a modern web UI.

**Backend Components:**
- WatchlistManager: JSON-based storage with multi-tenant support
- EpisodeChecker: Detects and downloads new episodes automatically
- AutoDownloadScheduler: APScheduler-based periodic task execution
- Complete REST API for CRUD operations and scheduler control

**Frontend Components:**
- Modern watchlist page with dark theme and animations
- Real-time status updates and progress tracking
- Scheduler controls with next-run display
- Add anime directly from search results

**Models & Configuration:**
- WatchlistItem with status, quality, and auto-download settings
- WatchlistSettings for global configuration
- Per-user statistics and provider tracking

**API Endpoints:**
- GET/POST /api/watchlist - List and add items
- PUT/DELETE /api/watchlist/{id} - Update and delete
- POST /api/watchlist/{id}/check - Manual check trigger
- POST /api/watchlist/check-all - Check all due items
- GET/PUT /api/watchlist/settings - Global settings
- GET /api/watchlist/stats - Statistics
- GET/POST /api/watchlist/scheduler/* - Scheduler control

**Configuration Files:**
- config/watchlist.json - User watchlist data
- config/watchlist_settings.json - Global settings

Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>

static/css/style.css

@@ -241,22 +241,24 @@
 
         .anime-card-actions {
             display: flex;
+            flex-direction: column;
             gap: 8px;
             margin-top: 15px;
         }
 
         .anime-card-actions select {
-            flex: 1;
+            width: 100%;
             padding: 8px;
             border: 2px solid rgba(255, 255, 255, 0.1);
             border-radius: 6px;
             background: rgba(0, 0, 0, 0.3);
             color: #fff;
             font-size: 13px;
+            box-sizing: border-box;
         }
 
         .anime-card-actions button {
-            flex: 1;
+            width: 100%;
             padding: 8px 12px;
             font-size: 12px;
         }