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/models/sonarr.py

@@ -160,7 +160,7 @@ class SonarrMapping(BaseModel):
     """Mapping between Sonarr series and anime providers (API model)"""
     sonarr_series_id: int
     sonarr_title: str
-    anime_provider: str  # 'anime-sama', 'neko-sama', etc.
+    anime_provider: str  # 'anime-sama', 'anime-ultime', 'vostfree', 'french-manga', etc.
     anime_url: str
     anime_title: str
     lang: str = "vostfr"