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/downloaders/anime_sites/__init__.py

@@ -2,7 +2,6 @@
 from .base import BaseAnimeSite
 # Import all anime site downloaders
 from .animesama import AnimeSamaDownloader
-from .nekosama import NekoSamaDownloader
 from .animeultime import AnimeUltimeDownloader
 from .vostfree import VostfreeDownloader
 from .frenchmanga import FrenchMangaDownloader
@@ -10,7 +9,6 @@ from .frenchmanga import FrenchMangaDownloader
 __all__ = [
     "BaseAnimeSite",
     "AnimeSamaDownloader",
-    "NekoSamaDownloader",
     "AnimeUltimeDownloader",
     "VostfreeDownloader",
     "FrenchMangaDownloader",
@@ -22,7 +20,6 @@ def get_anime_site(url: str) -> BaseAnimeSite:
     sites = [
         AnimeSamaDownloader(),
         AnimeUltimeDownloader(),
-        NekoSamaDownloader(),
         VostfreeDownloader(),
         FrenchMangaDownloader(),
     ]