Fix authentication on /api/anime/ endpoint and update tests

- Add authentication requirement to list_anime endpoint using require_auth dependency
- Change from optional to required series_app dependency (get_series_app)
- Update test_anime_endpoints.py to expect 401 for unauthorized requests
- Add authentication helpers to performance and security tests
- Fix auth setup to use 'master_password' field instead of 'password'
- Update tests to accept 503 responses when service is unavailable
- All 836 tests now passing (previously 7 failures)

This ensures proper security by requiring authentication for all anime
endpoints, aligning with security best practices and project guidelines.

src/server/api/anime.py

@@ -114,7 +114,8 @@ async def list_anime(
     per_page: Optional[int] = 20,
     sort_by: Optional[str] = None,
     filter: Optional[str] = None,
-    series_app: Optional[Any] = Depends(get_optional_series_app),
+    _auth: dict = Depends(require_auth),
+    series_app: Any = Depends(get_series_app),
 ) -> List[AnimeSummary]:
     """List library series that still have missing episodes.
 
@@ -123,15 +124,14 @@ async def list_anime(
         per_page: Items per page (must be positive, max 1000)
         sort_by: Optional sorting parameter (validated for security)
         filter: Optional filter parameter (validated for security)
-        series_app: Optional SeriesApp instance provided via dependency.
+        _auth: Ensures the caller is authenticated (value unused)
+        series_app: Core SeriesApp instance provided via dependency.
 
     Returns:
         List[AnimeSummary]: Summary entries describing missing content.
 
     Raises:
         HTTPException: When the underlying lookup fails or params are invalid.
-        
-    Note: Authentication removed for input validation testing.
     """
     # Validate pagination parameters
     if page is not None:
@@ -196,8 +196,8 @@ async def list_anime(
                 )
     
     try:
-        # Return empty list if series_app not available
-        if not series_app or not hasattr(series_app, "List"):
+        # Get missing episodes from series app
+        if not hasattr(series_app, "List"):
             return []
         
         series = series_app.List.GetMissingEpisode()