feat: mcp and backfill fixes

backend/src/userbot/modules/jobs/repository.py

@@ -79,13 +79,18 @@ async def finish(
 ) -> None:
     await pool.execute(
         "UPDATE jobs SET status = $2, error = $3, finished_at = now(), "
-        "updated_at = now() WHERE id = $1",
+        "updated_at = now() WHERE id = $1 AND status = 'running'",
         job_id,
         status.value,
         error,
     )
 
 
+async def is_canceled(pool: asyncpg.Pool, job_id: int) -> bool:
+    status = await pool.fetchval("SELECT status FROM jobs WHERE id = $1", job_id)
+    return status == JobStatus.CANCELED.value
+
+
 async def get_job(pool: asyncpg.Pool, job_id: int) -> Job | None:
     row = await pool.fetchrow("SELECT * FROM jobs WHERE id = $1", job_id)
     return _row_to_job(row) if row else None