feat(setup): track unresolved folders for manual key resolution

When SetupService cannot auto-resolve a provider key for an anime folder,
the folder is now tracked in the new 'unresolved_folders' table instead of
being silently skipped. Users can then resolve these via the new API:

- GET /api/setup/unresolved - list unresolved folders with search suggestions
- POST /api/setup/unresolved/{folder}/resolve - provide key to resolve folder

The SetupService.run() now:
- Tracks unresolved folders instead of skipping them
- Re-creates AnimeSeries for previously unresolved folders that are now resolved
- Includes unresolved count in logs

New files:
- src/server/api/setup_endpoints.py - API endpoints for unresolved management
- tests/unit/test_unresolved_folder_service.py - service and model tests

Modified:
- src/server/database/models.py - add UnresolvedFolder model
- src/server/database/service.py - add UnresolvedFolderService
- src/server/services/setup_service.py - track unresolved folders
- src/server/fastapi_app.py - include setup router

src/server/fastapi_app.py

@@ -27,6 +27,7 @@ from src.server.api.health import router as health_router
 from src.server.api.logging import router as logging_router
 from src.server.api.nfo import router as nfo_router
 from src.server.api.scheduler import router as scheduler_router
+from src.server.api.setup_endpoints import router as setup_router
 from src.server.api.websocket import router as websocket_router
 from src.server.controllers.error_controller import (
     not_found_handler,
@@ -648,6 +649,7 @@ app.include_router(scheduler_router)
 app.include_router(anime_router)
 app.include_router(download_router)
 app.include_router(nfo_router)
+app.include_router(setup_router)
 app.include_router(logging_router)
 app.include_router(websocket_router)