🚨 CRITICAL BREAKTHROUGH: Switch case for ListOffsets NEVER MATCHED!

## The Smoking Gun

Switch statement logging shows:
- 316 times: case APIKeyMetadata ✅
- 0 times: case APIKeyListOffsets (apiKey=2) ❌❌❌
- 6+ times: case APIKeyApiVersions ✅

## What This Means

The case label for APIKeyListOffsets is NEVER executed, meaning:

1. ✅ TCP receives requests with apiKey=2
2. ✅ REQUEST_LOOP parses and logs them as apiKey=2
3. ✅ Requests are queued to channel
4. ❌ processRequestSync receives a DIFFERENT apiKey value than 2!

OR

The apiKey=2 requests are being ROUTED ELSEWHERE before reaching processRequestSync switch statement!

## Root Cause

The apiKey value is being MODIFIED or CORRUPTED between:
- HTTP-level request parsing (REQUEST_LOOP logs show 2)
- Request queuing
- processRequestSync switch statement execution

OR the requests are being routed to a different channel (data plane vs control plane)
and never reaching the Sync handler!

## Next: Check request routing logic to see if apiKey=2 is being sent to wrong channel

weed/mq/kafka/protocol/handler.go

@@ -1112,12 +1112,15 @@ func (h *Handler) processRequestSync(req *kafkaRequest) ([]byte, error) {
 
 	switch APIKey(req.apiKey) {
 	case APIKeyApiVersions:
+		glog.Warningf("🔥 SWITCH MATCHED: APIKeyApiVersions")
 		response, err = h.handleApiVersions(req.correlationID, req.apiVersion)
 
 	case APIKeyMetadata:
+		glog.Warningf("🔥 SWITCH MATCHED: APIKeyMetadata")
 		response, err = h.handleMetadata(req.correlationID, req.apiVersion, req.requestBody)
 
 	case APIKeyListOffsets:
+		glog.Warningf("🔥🔥🔥 SWITCH MATCHED: APIKeyListOffsets (apiKey=2)!!!")
 		glog.Warningf("🟡 processRequestSync: Handling ListOffsets (apiKey=2) - about to call handleListOffsets")
 		response, err = h.handleListOffsets(req.correlationID, req.apiVersion, req.requestBody)