feat: Add optional web interface authentication with session management

Authentication Features:
  - Optional HTTP Basic Auth with session cookies for web interface protection
  - Configurable username/password with session timeout (default: 1 hour)
  - Selective route protection (web interface protected, webhooks/APIs remain public)
  - Authentication status display with logout functionality in web UI
  - Session cleanup and graceful logout with browser re-authentication prompt

  Configuration:
  - WEB_AUTH_ENABLED in .env (default: false - no breaking changes)
  - WEB_AUTH_USERNAME/WEB_AUTH_PASSWORD in .env.secrets
  - WEB_AUTH_SESSION_TIMEOUT configurable (5min-24h range)

  Development Tools:
  - Added debug_tv.py for TV series/episode debugging (series, season, episode levels)
  - Comprehensive episode data inspection with validation and sources breakdown
  - Complements existing debug_movie.py for complete media debugging coverage

  Technical Implementation:
  - SimpleAuthMiddleware with FastAPI integration
  - Session management with automatic cleanup
  - Authentication status API endpoints
  - Responsive CSS styling for auth UI elements
  - JavaScript functions for auth checking and logout

.env.secrets.example

@@ -38,4 +38,12 @@ JELLYSEERR_API_KEY=your_jellyseerr_api_key
 # TVDB API key (RECOMMENDED for v0.6.1+ Emby TV NFO Compatibility)
 # Required to convert IMDB IDs to TVDB IDs for proper Emby metadata loading
 # Get free API key at: https://thetvdb.com/api-information
-TVDB_API_KEY=your_tvdb_api_key
+TVDB_API_KEY=your_tvdb_api_key
+
+# ===========================================
+# WEB INTERFACE AUTHENTICATION (OPTIONAL)
+# ===========================================
+# Web interface login credentials (only used if WEB_AUTH_ENABLED=true in .env)
+# Set WEB_AUTH_ENABLED=true in .env file to enable authentication
+WEB_AUTH_USERNAME=admin
+WEB_AUTH_PASSWORD=your_secure_web_password