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

static/css/styles.css

@@ -39,6 +39,7 @@ body {
     color: white;
     padding: 1rem 0;
     box-shadow: var(--shadow-lg);
+    position: relative;
 }
 
 .header-content {
@@ -63,6 +64,45 @@ body {
     font-size: 1rem;
 }
 
+/* Authentication Status */
+.auth-status {
+    position: absolute;
+    top: 1rem;
+    right: 1rem;
+    display: flex;
+    align-items: center;
+    gap: 1rem;
+    color: white;
+    font-size: 0.9rem;
+}
+
+.auth-user {
+    display: flex;
+    align-items: center;
+    gap: 0.5rem;
+    opacity: 0.9;
+}
+
+.auth-logout {
+    background: rgba(255, 255, 255, 0.2);
+    color: white;
+    border: 1px solid rgba(255, 255, 255, 0.3);
+    padding: 0.5rem 1rem;
+    border-radius: 0.25rem;
+    cursor: pointer;
+    font-size: 0.85rem;
+    display: flex;
+    align-items: center;
+    gap: 0.5rem;
+    transition: all 0.2s ease;
+}
+
+.auth-logout:hover {
+    background: rgba(255, 255, 255, 0.3);
+    border-color: rgba(255, 255, 255, 0.5);
+    transform: translateY(-1px);
+}
+
 .nav-tabs {
     max-width: 1200px;
     margin: 1rem auto 0;