feat: 更新主流大模型供应商目录

- 按云服务、Coding Plan、API 网关和本地模型分组

- 新增兼容模型发现与供应商协议校验

backend/controller/llm_chat.go

@@ -195,10 +195,11 @@ func (h *LLMHandler) llmConfigFromTestRequest(req model.SaveLLMConfigRequest) (m
 	}
 	if strings.Contains(req.APIKey, "****") {
 		var saved model.LLMConfig
-		if err := h.db.First(&saved).Error; err != nil {
+		if err := h.db.Take(&saved).Error; err != nil || !canReuseMaskedAPIKey(req.Provider, req.Endpoint, saved) {
 			if !isLocalLLMProvider(req.Provider) {
-				return cfg, "请填写 API Key"
+				return cfg, "提供商或 Endpoint 已变化，请重新填写 API Key"
 			}
+			cfg.APIKey = ""
 		} else {
 			cfg.APIKey = saved.APIKey
 		}
@@ -209,6 +210,9 @@ func (h *LLMHandler) llmConfigFromTestRequest(req model.SaveLLMConfigRequest) (m
 	if cfg.Model == "" {
 		return cfg, "请填写模型名"
 	}
+	if requiresExplicitEndpoint(cfg.Provider) && strings.TrimSpace(cfg.Endpoint) == "" {
+		return cfg, "请填写 Endpoint"
+	}
 	if cfg.APIKey == "" && !isLocalLLMProvider(cfg.Provider) {
 		return cfg, "请填写 API Key"
 	}
@@ -226,7 +230,7 @@ func (h *LLMHandler) TestLLMConnection(c *gin.Context) {
 	if req.Provider != "" {
 		cfg, errMsg = h.llmConfigFromTestRequest(req)
 	} else {
-		if err := h.db.First(&cfg).Error; err != nil {
+		if err := h.db.Take(&cfg).Error; err != nil {
 			c.JSON(http.StatusOK, model.Response{Code: 400, Message: "请先填写配置并测试连接"})
 			return
 		}