mq(kafka): CRITICAL Discovery - Issue not v7-specific, persists in Metadata v1

MAJOR BREAKTHROUGH:
❌ Same 'Unknown Topic Or Partition' error occurs with Metadata v1
✅ This proves issue is NOT related to v7-specific fields
✅ kafka-go correctly negotiates down from v7 → v1

EVIDENCE:
- Response size: 120 bytes (v7) → 95 bytes (v1) ✅
- Version negotiation: API 3 v1 requested ✅
- Same error pattern: kafka-go validates → rejects → retries ❌

HYPOTHESIS IDENTIFIED:
🎯 Port/Address Mismatch Issue:
- kafka-go connects to gateway on random port (:60364)
- Metadata response advertises broker at localhost:9092
- kafka-go may be trying to validate broker reachability

CURRENT STATUS:
The issue is fundamental to our Metadata response format, not version-specific.
kafka-go likely validates that advertised brokers are reachable before
proceeding to Produce operations.

NEXT: Fix broker address in Metadata to match actual gateway listening port.

weed/mq/kafka/protocol/handler.go

@@ -270,9 +270,10 @@ func (h *Handler) handleApiVersions(correlationID uint32) ([]byte, error) {
 	response = append(response, 0, 3)  // max version 3
 
 	// API Key 3 (Metadata): api_key(2) + min_version(2) + max_version(2)
+	// TEMP: Limit to v1 to test if issue is v7-specific
 	response = append(response, 0, 3) // API key 3
 	response = append(response, 0, 0) // min version 0
-	response = append(response, 0, 7) // max version 7
+	response = append(response, 0, 1) // max version 1 (instead of 7)
 
 	// API Key 2 (ListOffsets): api_key(2) + min_version(2) + max_version(2)
 	response = append(response, 0, 2) // API key 2
@@ -360,7 +361,7 @@ func (h *Handler) handleMetadata(correlationID uint32, requestBody []byte) ([]by
 	// Use "localhost" for simplicity - kafka-go should be able to connect back
 	// The port issue is more likely the problem than the host
 	host := "localhost"
-	
+
 	response = append(response, 0, byte(len(host)))
 	response = append(response, []byte(host)...)
 
@@ -377,9 +378,8 @@ func (h *Handler) handleMetadata(correlationID uint32, requestBody []byte) ([]by
 	// Controller ID (4 bytes) - -1 (no controller)
 	response = append(response, 0xFF, 0xFF, 0xFF, 0xFF)
 
-	// Cluster authorized operations (4 bytes) - For Metadata v7+
-	// -1 = not supported/null
-	response = append(response, 0xFF, 0xFF, 0xFF, 0xFF)
+	// TEMP: Removed v7+ fields to test with Metadata v1
+	// Cluster authorized operations removed for v1 compatibility
 
 	// Parse topics from request (for metadata discovery)
 	requestedTopics := h.parseMetadataTopics(requestBody)
@@ -423,12 +423,9 @@ func (h *Handler) handleMetadata(correlationID uint32, requestBody []byte) ([]by
 		binary.BigEndian.PutUint16(topicNameLen, uint16(len(topicNameBytes)))
 		response = append(response, topicNameLen...)
 		response = append(response, topicNameBytes...)
-
-		// Topic UUID (16 bytes) - For Metadata v7+, using null UUID (all zeros)
-		response = append(response, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)
-
-		// Is internal topic (1 byte) - false
-		response = append(response, 0)
+		
+		// TEMP: Removed v7+ fields for v1 compatibility
+		// Topic UUID and is_internal_topic removed
 
 		// Partitions array length (4 bytes) - 1 partition
 		response = append(response, 0, 0, 0, 1)
@@ -440,10 +437,8 @@ func (h *Handler) handleMetadata(correlationID uint32, requestBody []byte) ([]by
 		response = append(response, 0, 0, 0, 0)             // leader_id = 0 (this broker)
 		response = append(response, 0, 0, 0, 1, 0, 0, 0, 0) // replicas = [0]
 		response = append(response, 0, 0, 0, 1, 0, 0, 0, 0) // isr = [0]
-
-		// Topic authorized operations (4 bytes) - For Metadata v7+
-		// -1 = not supported/null
-		response = append(response, 0xFF, 0xFF, 0xFF, 0xFF)
+		
+		// TEMP: Removed v7+ topic authorized operations for v1 compatibility
 	}
 
 	fmt.Printf("DEBUG: Metadata response for %d topics: %v\n", len(topicsToReturn), topicsToReturn)