Remove Shikimori API, use AnimeThemes only, switch to WebM format

- Remove ShikimoriService, use AnimeThemes API for search
- Replace shikimori_id with animethemes_slug as primary identifier
- Remove FFmpeg MP3 conversion, download WebM directly
- Add .webm support in storage and upload endpoints
- Update frontend to use animethemes_slug

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

backend/app/openings_downloader/router.py

@@ -21,7 +21,6 @@ from .schemas import (
     StorageStatsResponse,
 )
 from .db_models import Anime, AnimeTheme, DownloadTask, DownloadStatus
-from .services.shikimori import ShikimoriService
 from .services.animethemes import AnimeThemesService
 from .services.downloader import DownloadService
 from .services.storage_tracker import StorageTrackerService
@@ -34,30 +33,29 @@ router = APIRouter(prefix="/downloader", tags=["openings-downloader"])
 @router.get("/search", response_model=SearchResponse)
 async def search_anime(
     query: str = Query(..., min_length=1, description="Search query"),
-    year: Optional[int] = Query(None, description="Filter by year"),
-    status: Optional[str] = Query(None, description="Filter by status (ongoing, released, announced)"),
     limit: int = Query(20, ge=1, le=50, description="Maximum results"),
     db: AsyncSession = Depends(get_db),
 ):
-    """Search anime via Shikimori API."""
-    service = ShikimoriService()
-    results = await service.search(query, year=year, status=status, limit=limit)
+    """Search anime via AnimeThemes API."""
+    service = AnimeThemesService()
+    results = await service.search(query, limit=limit)
     return SearchResponse(results=results, total=len(results))
 
 
 # ============== Anime Detail ==============
 
-@router.get("/anime/{shikimori_id}", response_model=AnimeDetailResponse)
+@router.get("/anime/{slug:path}", response_model=AnimeDetailResponse)
 async def get_anime_detail(
-    shikimori_id: int,
+    slug: str,
     db: AsyncSession = Depends(get_db),
 ):
     """Get anime details with available themes from AnimeThemes."""
-    shikimori_service = ShikimoriService()
     animethemes_service = AnimeThemesService()
 
     # Get or create anime record
-    anime = await shikimori_service.get_or_create_anime(db, shikimori_id)
+    anime = await animethemes_service.get_or_create_anime(db, slug)
+    if not anime:
+        raise HTTPException(status_code=404, detail=f"Anime not found: {slug}")
 
     # Fetch themes from AnimeThemes API
     themes = await animethemes_service.fetch_themes(db, anime)
@@ -92,10 +90,8 @@ async def get_anime_detail(
 
     return AnimeDetailResponse(
         id=anime.id,
-        shikimori_id=anime.shikimori_id,
-        title_russian=anime.title_russian,
+        animethemes_slug=anime.animethemes_slug,
         title_english=anime.title_english,
-        title_japanese=anime.title_japanese,
         year=anime.year,
         poster_url=anime.poster_url,
         themes=theme_infos,