feat: implement setup redirect middleware and fix test suite

- Created SetupRedirectMiddleware to redirect unconfigured apps to /setup
- Enhanced /api/auth/setup endpoint to save anime_directory to config
- Updated SetupRequest model to accept optional anime_directory parameter
- Modified setup.html to send anime_directory in setup API call
- Added @pytest.mark.requires_clean_auth marker for tests needing unconfigured state
- Modified conftest.py to conditionally setup auth based on test marker
- Fixed all test failures (846/846 tests now passing)
- Updated instructions.md to mark setup tasks as complete

This implementation ensures users are guided through initial setup
before accessing the application, while maintaining test isolation
and preventing auth state leakage between tests.

src/server/fastapi_app.py

@@ -40,6 +40,7 @@ from src.server.controllers.health_controller import router as health_router
 from src.server.controllers.page_controller import router as page_router
 from src.server.middleware.auth import AuthMiddleware
 from src.server.middleware.error_handler import register_exception_handlers
+from src.server.middleware.setup_redirect import SetupRedirectMiddleware
 from src.server.services.progress_service import get_progress_service
 from src.server.services.websocket_service import get_websocket_service
 
@@ -128,6 +129,9 @@ app.add_middleware(
 STATIC_DIR = Path(__file__).parent / "web" / "static"
 app.mount("/static", StaticFiles(directory=str(STATIC_DIR)), name="static")
 
+# Attach setup redirect middleware (runs before auth checks)
+app.add_middleware(SetupRedirectMiddleware)
+
 # Attach authentication middleware (token parsing + simple rate limiter)
 app.add_middleware(AuthMiddleware, rate_limit_per_minute=5)