fix: final review wave — CLI kwargs, class filter, job locks, upload order, tests

tests/test_app.py

@@ -1,5 +1,7 @@
 """Integration tests for Flask web app."""
 
+import io
+
 import pytest
 from app import app
 
@@ -45,6 +47,16 @@ def test_upload_no_video(client):
     assert resp.status_code == 400
 
 
+def test_upload_invalid_extension_rejected(client):
+    """POST /upload with a non-video file returns 400."""
+    resp = client.post(
+        "/upload",
+        data={"video": (io.BytesIO(b"not a video"), "notes.txt")},
+        content_type="multipart/form-data",
+    )
+    assert resp.status_code == 400
+
+
 def test_status_nonexistent(client):
     """GET /status/nonexistent returns 404."""
     resp = client.get("/status/nonexistent")