Fix: Remove episodes from missing list on download/rescan

- Update _update_series_in_db to sync missing episodes bidirectionally
- Add delete_by_series_and_episode method to EpisodeService
- Remove downloaded episodes from DB after successful download
- Clear anime service cache when episodes are removed
- Fix tests to use 'message' instead of 'detail' in API responses
- Mock DB operations in rescan tests

tests/api/test_download_endpoints.py

@@ -236,7 +236,7 @@ async def test_add_to_queue_service_error(
     )
 
     assert response.status_code == 400
-    assert "Queue full" in response.json()["detail"]
+    assert "Queue full" in response.json()["message"]
 
 
 @pytest.mark.asyncio
@@ -294,8 +294,8 @@ async def test_start_download_empty_queue(
 
     assert response.status_code == 400
     data = response.json()
-    detail = data["detail"].lower()
-    assert "empty" in detail or "no pending" in detail
+    message = data["message"].lower()
+    assert "empty" in message or "no pending" in message
 
 
 @pytest.mark.asyncio
@@ -311,8 +311,8 @@ async def test_start_download_already_active(
 
     assert response.status_code == 400
     data = response.json()
-    detail_lower = data["detail"].lower()
-    assert "already" in detail_lower or "progress" in detail_lower
+    message_lower = data["message"].lower()
+    assert "already" in message_lower or "progress" in message_lower
 
 
 @pytest.mark.asyncio