🔧 **fix(model, controller): robust serialization for ChannelInfo & correct Vertex-AI key storage**

Summary
1. **model/channel.go**
   • Replaced the pointer-only `Value()` with a value-receiver implementation
   • GORM can now marshal both `ChannelInfo` and `*ChannelInfo`, eliminating
     `unsupported type model.ChannelInfo` runtime error.

2. **controller/channel.go**
   • Refactored `getVertexArrayKeys()` – every element is now
     - passed through `json.Marshal` when not already a string
     - trimmed & validated before insertion
   • Guarantees each service-account key is persisted as a **pure JSON string**
     instead of the previous `map[...]` dump.

Result
• Channel creation / update succeeds without SQL driver errors.
• Vertex-AI batch & multi-key uploads are stored in canonical JSON, ready for
  downstream SDKs to consume.

controller/channel.go

@@ -394,9 +394,19 @@ func getVertexArrayKeys(keys string) ([]string, error) {
 	}
 	cleanKeys := make([]string, 0, len(keyArray))
 	for _, key := range keyArray {
-		keyStr := fmt.Sprintf("%v", key)
+		var keyStr string
+		switch v := key.(type) {
+		case string:
+			keyStr = strings.TrimSpace(v)
+		default:
+			bytes, err := json.Marshal(v)
+			if err != nil {
+				return nil, fmt.Errorf("Vertex AI key JSON 编码失败: %w", err)
+			}
+			keyStr = string(bytes)
+		}
 		if keyStr != "" {
-			cleanKeys = append(cleanKeys, strings.TrimSpace(keyStr))
+			cleanKeys = append(cleanKeys, keyStr)
 		}
 	}
 	if len(cleanKeys) == 0 {