feat(copilot): finish configuration center

backend/internal/handler/api/v1/sse_stream_handler.go

@@ -88,7 +88,7 @@ func (h *SSEStreamHandler) StreamCopilotMessage(c *gin.Context) {
 		return
 	}
 	if h.llmProvider == nil {
-		writeSSEMessage(c, "error", `{"error": "Captain is disabled", "status": 422, "done": true}`)
+		writeSSEMessage(c, "error", `{"code": "COPILOT_NOT_CONFIGURED", "error": "Copilot provider is not configured", "status": 503, "done": true}`)
 		writeSSEMessage(c, "done", `{"done": true}`)
 		return
 	}
@@ -98,14 +98,15 @@ func (h *SSEStreamHandler) StreamCopilotMessage(c *gin.Context) {
 
 	// Stream from LLM using callback pattern
 	streamReq := llm.ChatRequest{
-		Model:       "gpt-4",
+		Model:       "",
 		Messages:    chatMessages,
 		Temperature: 0.7,
 		MaxTokens:   1024,
 		Stream:      true,
 	}
 
-	err = h.llmProvider.ChatCompletionStream(c.Request.Context(), streamReq, func(chunk llm.StreamChunk) error {
+	streamCtx := llm.WithAccountFeature(c.Request.Context(), uint(accountID), "copilot")
+	err = h.llmProvider.ChatCompletionStream(streamCtx, streamReq, func(chunk llm.StreamChunk) error {
 		if len(chunk.Choices) > 0 {
 			content := chunk.Choices[0].Delta.Content
 			if content != "" {