feat(account): 账号测试支持选择模型

- 新增 GET /api/v1/admin/accounts/:id/models 接口获取账号可用模型
- 账号测试弹窗新增模型选择下拉框
- 测试时支持传入 model_id 参数，不传则默认使用 Sonnet
- API Key 账号支持根据 model_mapping 映射测试模型
- 将模型常量提取到 claude 包统一管理

backend/internal/handler/admin/account_handler.go

@@ -3,6 +3,7 @@ package admin
 import (
 	"strconv"
 
+	"sub2api/internal/pkg/claude"
 	"sub2api/internal/pkg/response"
 	"sub2api/internal/service"
 
@@ -186,6 +187,11 @@ func (h *AccountHandler) Delete(c *gin.Context) {
 	response.Success(c, gin.H{"message": "Account deleted successfully"})
 }
 
+// TestAccountRequest represents the request body for testing an account
+type TestAccountRequest struct {
+	ModelID string `json:"model_id"`
+}
+
 // Test handles testing account connectivity with SSE streaming
 // POST /api/v1/admin/accounts/:id/test
 func (h *AccountHandler) Test(c *gin.Context) {
@@ -195,8 +201,12 @@ func (h *AccountHandler) Test(c *gin.Context) {
 		return
 	}
 
+	var req TestAccountRequest
+	// Allow empty body, model_id is optional
+	_ = c.ShouldBindJSON(&req)
+
 	// Use AccountTestService to test the account with SSE streaming
-	if err := h.accountTestService.TestAccountConnection(c, accountID); err != nil {
+	if err := h.accountTestService.TestAccountConnection(c, accountID, req.ModelID); err != nil {
 		// Error already sent via SSE, just log
 		return
 	}
@@ -535,3 +545,58 @@ func (h *AccountHandler) SetSchedulable(c *gin.Context) {
 
 	response.Success(c, account)
 }
+
+// GetAvailableModels handles getting available models for an account
+// GET /api/v1/admin/accounts/:id/models
+func (h *AccountHandler) GetAvailableModels(c *gin.Context) {
+	accountID, err := strconv.ParseInt(c.Param("id"), 10, 64)
+	if err != nil {
+		response.BadRequest(c, "Invalid account ID")
+		return
+	}
+
+	account, err := h.adminService.GetAccount(c.Request.Context(), accountID)
+	if err != nil {
+		response.NotFound(c, "Account not found")
+		return
+	}
+
+	// For OAuth and Setup-Token accounts: return default models
+	if account.IsOAuth() {
+		response.Success(c, claude.DefaultModels)
+		return
+	}
+
+	// For API Key accounts: return models based on model_mapping
+	mapping := account.GetModelMapping()
+	if mapping == nil || len(mapping) == 0 {
+		// No mapping configured, return default models
+		response.Success(c, claude.DefaultModels)
+		return
+	}
+
+	// Return mapped models (keys of the mapping are the available model IDs)
+	var models []claude.Model
+	for requestedModel := range mapping {
+		// Try to find display info from default models
+		var found bool
+		for _, dm := range claude.DefaultModels {
+			if dm.ID == requestedModel {
+				models = append(models, dm)
+				found = true
+				break
+			}
+		}
+		// If not found in defaults, create a basic entry
+		if !found {
+			models = append(models, claude.Model{
+				ID:          requestedModel,
+				Type:        "model",
+				DisplayName: requestedModel,
+				CreatedAt:   "",
+			})
+		}
+	}
+
+	response.Success(c, models)
+}