debug: Add consumer coordination logging to pinpoint consumer init issue

Added logging for consumer group coordination API keys (9,11,12,14) to identify
where consumer gets stuck during initialization.

KEY FINDING: Consumer is NOT stuck in group coordination!
Instead, consumer is stuck in seek/metadata discovery phase.

Evidence from test logs:
- Metadata (apiKey=3): 2,137 requests ✅
- ApiVersions (apiKey=18): 22 requests ✅
- ListOffsets (apiKey=2): 6 requests ✅ (but not completing!)
- JoinGroup (apiKey=11): 0 requests ❌
- SyncGroup (apiKey=14): 0 requests ❌
- Fetch (apiKey=1): 0 requests ❌

Consumer is stuck trying to execute seekToBeginning():
1. Consumer.assign() succeeds
2. Consumer.seekToBeginning() called
3. Consumer sends ListOffsets request (succeeds)
4. Stuck waiting for metadata or broker connection
5. Consumer.poll() never called
6. Initialization never completes

Root cause likely in:
- ListOffsets (apiKey=2) response format or content
- Metadata response broker assignment
- Partition leader discovery

This is separate from the context timeout bug (Bug #1).
Both must be fixed for Schema Registry to work.

.gitignore

@@ -123,3 +123,4 @@ ADVANCED_IAM_DEVELOPMENT_PLAN.md
 /test/s3/iam/test-volume-data
 *.log
 weed-iam
+test/kafka/kafka-client-loadtest/weed-linux-arm64

weed/mq/kafka/protocol/handler.go

@@ -934,6 +934,18 @@ func (h *Handler) HandleConn(ctx context.Context, conn net.Conn) error {
 		glog.V(4).Infof("API version validated: Key=%d (%s), Version=%d, Correlation=%d",
 			apiKey, getAPIName(APIKey(apiKey)), apiVersion, correlationID)
 
+		// Log consumer group coordination requests
+		switch apiKey {
+		case 9:
+			glog.Warningf("🟡 OffsetFetch: correlationID=%d from %s", correlationID, connectionID)
+		case 11:
+			glog.Warningf("🟡 JoinGroup: correlationID=%d from %s", correlationID, connectionID)
+		case 12:
+			glog.Warningf("🟡 Heartbeat: correlationID=%d from %s", correlationID, connectionID)
+		case 14:
+			glog.Warningf("🟡 SyncGroup: correlationID=%d from %s", correlationID, connectionID)
+		}
+
 		// Extract request body - special handling for ApiVersions requests
 		var requestBody []byte
 		if apiKey == uint16(APIKeyApiVersions) && apiVersion >= 3 {