feat(proxy): Adds last activity time tracking for streaming responses

Adds a `lastActivityAt` field to the `streamingResponseEntry` structure to record the last active time of the streaming response.

Updates this timestamp when creating the streaming response, sending headers, and sending data blocks.

Modifies the logic for cleaning up timeout channels, using the last activity time instead of the creation time to determine if a timeout has occurred, improving accuracy in long-connection scenarios.

internal/server/proxy/response_handler.go

@@ -20,12 +20,13 @@ type responseChanEntry struct {
 
 // streamingResponseEntry holds a streaming response writer
 type streamingResponseEntry struct {
-	w           http.ResponseWriter
-	flusher     http.Flusher
-	createdAt   time.Time
-	headersSent bool
-	done        chan struct{}
-	mu          sync.Mutex
+	w              http.ResponseWriter
+	flusher        http.Flusher
+	createdAt      time.Time
+	lastActivityAt time.Time
+	headersSent    bool
+	done           chan struct{}
+	mu             sync.Mutex
 }
 
 // ResponseHandler manages response channels for HTTP requests over TCP/Frame protocol
@@ -73,11 +74,13 @@ func (h *ResponseHandler) CreateStreamingResponse(requestID string, w http.Respo
 
 	flusher, _ := w.(http.Flusher)
 	done := make(chan struct{})
+	now := time.Now()
 	h.streamingChannels[requestID] = &streamingResponseEntry{
-		w:         w,
-		flusher:   flusher,
-		createdAt: time.Now(),
-		done:      done,
+		w:              w,
+		flusher:        flusher,
+		createdAt:      now,
+		lastActivityAt: now,
+		done:           done,
 	}
 
 	return done
@@ -176,6 +179,7 @@ func (h *ResponseHandler) SendStreamingHead(requestID string, head *protocol.HTT
 
 	entry.w.WriteHeader(statusCode)
 	entry.headersSent = true
+	entry.lastActivityAt = time.Now()
 
 	if entry.flusher != nil {
 		entry.flusher.Flush()
@@ -221,6 +225,8 @@ func (h *ResponseHandler) SendStreamingChunk(requestID string, chunk []byte, isL
 			return nil
 		}
 
+		entry.lastActivityAt = time.Now()
+
 		if entry.flusher != nil {
 			entry.flusher.Flush()
 		}
@@ -321,7 +327,7 @@ func (h *ResponseHandler) cleanupExpiredChannels() {
 	}
 
 	for requestID, entry := range h.streamingChannels {
-		if now.Sub(entry.createdAt) > streamingTimeout {
+		if now.Sub(entry.lastActivityAt) > streamingTimeout {
 			select {
 			case <-entry.done:
 			default: