fix(api): await Kafka acknowledgements and bound HTTP requests

app/worker/dlq.py

@@ -28,6 +28,8 @@ def build_dlq_envelope(
     """
     Constructs a standardized DLQ envelope according to specification.
     """
+    if failure_reason not in ALLOWED_FAILURE_REASONS:
+        raise ValueError(f"Unsupported DLQ reason: {failure_reason}")
     return {
         "original_payload": original_payload,
         "failure_reason": failure_reason,
@@ -56,11 +58,13 @@ def route_to_dlq(
     )
     envelope_bytes = json.dumps(envelope, default=str).encode("utf-8")
 
-    success = producer.produce(topic=topic, key=raw_id, value=envelope_bytes)
+    producer.produce(topic=topic, key=raw_id, value=envelope_bytes).result(
+        timeout=config.kafka.delivery_timeout_seconds + 1
+    )
     worker_metrics.record_dlq(failure_reason, 1)
 
     logger.warning(
         f"Record routed to DLQ: reason={failure_reason}, field={failed_field}",
         extra={"raw_id": raw_id, "event": "routed_to_dlq"},
     )
-    return success
+    return True