fix: migrations, auth, providers health check, E2E tests, remove neko-sama

- Add proper Alembic initial migration (0001_initial_schema.py)
- Migrate refresh tokens from JSON file to SQLite (RefreshTokenTable)
- Remove Neko-Sama provider entirely (redirects to Gupy, not a host)
- Fix provider health check always showing UNKNOWN
  - Run check_all_health() on startup
  - Fix POST /providers/health/check background task bug
  - Add HTMX refresh after manual health check trigger
- Fix anime search relevance scoring with MIN_RELEVANCE_THRESHOLD=0.5
- Replace bare 'except:' with 'except Exception:' across codebase
- Add Playwright E2E test suite (12 tests, auth setup, helpers)
- Fix toast container blocking clicks via pointer-events: none
- Remove obsolete Jest/Vite test files and config
- Clean up obsolete test_watchlist scripts
- Update sonarr model comment for active providers

app/providers.py

@@ -25,13 +25,6 @@ ANIME_PROVIDERS = {
         "icon": "▶️",
         "color": "#00ff88",
     },
-    "neko-sama": {
-        "name": "Neko-Sama",
-        "domains": ["neko-sama.fr", "nekosama.fr", "www.neko-sama.fr"],
-        "url_pattern": "https://neko-sama.fr/anime/{slug}",
-        "icon": "🐱",
-        "color": "#ff6b6b",
-    },
     "vostfree": {
         "name": "Vostfree",
         "domains": ["vostfree.tv", "www.vostfree.tv"],