feat: add video job cancellation functionality and error tracking in generated videos

Co-authored-by: Copilot <copilot@github.com>

backend/app/routers/generate.py

@@ -322,7 +322,7 @@ async def list_generated_videos(
     user_id = current_user.get("id") or current_user.get("sub")
     conn = get_conn()
     rows = conn.execute(
-        """SELECT id, job_id, model_id, prompt, polling_url, status, video_url, created_at
+        """SELECT id, job_id, model_id, prompt, polling_url, status, video_url, error, created_at
            FROM generated_videos
            WHERE user_id = ?
            ORDER BY created_at DESC""",
@@ -337,7 +337,8 @@ async def list_generated_videos(
             "polling_url": r[4],
             "status": r[5],
             "video_url": r[6],
-            "created_at": r[7].isoformat() if r[7] else None,
+            "error": r[7],
+            "created_at": r[8].isoformat() if r[8] else None,
         }
         for r in rows
     ]
@@ -352,7 +353,7 @@ async def get_generated_video(
     user_id = current_user.get("id") or current_user.get("sub")
     conn = get_conn()
     row = conn.execute(
-        """SELECT id, job_id, model_id, prompt, polling_url, status, video_url, created_at, updated_at
+        """SELECT id, job_id, model_id, prompt, polling_url, status, video_url, error, created_at, updated_at
            FROM generated_videos
            WHERE id = ? AND user_id = ?""",
         [video_id, user_id],
@@ -367,6 +368,36 @@ async def get_generated_video(
         "polling_url": row[4],
         "status": row[5],
         "video_url": row[6],
-        "created_at": row[7].isoformat() if row[7] else None,
-        "updated_at": row[8].isoformat() if row[8] else None,
+        "error": row[7],
+        "created_at": row[8].isoformat() if row[8] else None,
+        "updated_at": row[9].isoformat() if row[9] else None,
     }
+
+
+@router.post("/videos/{video_id}/cancel", status_code=200)
+async def cancel_video_job(
+    video_id: str,
+    current_user: dict = Depends(get_current_user),
+) -> dict[str, str]:
+    """Mark a video job as 'cancelled' if it belongs to the current user and is not terminal."""
+    user_id = current_user.get("id") or current_user.get("sub")
+    conn = get_conn()
+    row = conn.execute(
+        "SELECT status FROM generated_videos WHERE id = ? AND user_id = ?",
+        [video_id, user_id],
+    ).fetchone()
+    if not row:
+        raise HTTPException(status_code=404, detail="Video job not found")
+    job_status = row[0]
+    if job_status in ("completed", "failed", "cancelled"):
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f"Cannot cancel job with status '{job_status}'",
+        )
+    now = datetime.now(timezone.utc).replace(tzinfo=None)
+    async with get_write_lock():
+        conn.execute(
+            "UPDATE generated_videos SET status = 'cancelled', updated_at = ? WHERE id = ?",
+            [now, video_id],
+        )
+    return {"status": "ok", "job_id": video_id}