fix(Antigravity): 支持无 project_id 的账户类型

- 移除 project_id 强制检查，部分账户类型 API 不返回此字段
- 重构：提取 antigravity.NewAPIRequest() 统一创建 API 请求
- quota_refresher: 无 project_id 时仍可更新 tier 信息

backend/internal/pkg/antigravity/client.go

 package antigravity
 
 import (
+	"bytes"
 	"context"
 	"encoding/json"
 	"fmt"
@@ -11,6 +12,19 @@ import (
 	"time"
 )
 
+// NewAPIRequest 创建 Antigravity API 请求（v1internal 端点）
+func NewAPIRequest(ctx context.Context, action, accessToken string, body []byte) (*http.Request, error) {
+	apiURL := fmt.Sprintf("%s/v1internal:%s", BaseURL, action)
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, apiURL, bytes.NewReader(body))
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("Authorization", "Bearer "+accessToken)
+	req.Header.Set("User-Agent", UserAgent)
+	return req, nil
+}
+
 // TokenResponse Google OAuth token 响应
 type TokenResponse struct {
 	AccessToken  string `json:"access_token"`

backend/internal/service/antigravity_gateway_service.go

@@ -148,11 +148,8 @@ func (s *AntigravityGatewayService) TestConnection(ctx context.Context, account
 		return nil, fmt.Errorf("获取 access_token 失败: %w", err)
 	}
 
-	// 获取 project_id
+	// 获取 project_id（部分账户类型可能没有）
 	projectID := strings.TrimSpace(account.GetCredential("project_id"))
-	if projectID == "" {
-		return nil, errors.New("project_id not found in credentials")
-	}
 
 	// 模型映射
 	mappedModel := s.getMappedModel(account, modelID)
@@ -171,14 +168,10 @@ func (s *AntigravityGatewayService) TestConnection(ctx context.Context, account
 	}
 
 	// 构建 HTTP 请求（非流式）
-	fullURL := fmt.Sprintf("%s/v1internal:generateContent", antigravity.BaseURL)
-	req, err := http.NewRequestWithContext(ctx, http.MethodPost, fullURL, bytes.NewReader(requestBody))
+	req, err := antigravity.NewAPIRequest(ctx, "generateContent", accessToken, requestBody)
 	if err != nil {
 		return nil, err
 	}
-	req.Header.Set("Content-Type", "application/json")
-	req.Header.Set("Authorization", "Bearer "+accessToken)
-	req.Header.Set("User-Agent", antigravity.UserAgent)
 
 	// 代理 URL
 	proxyURL := ""
@@ -350,11 +343,8 @@ func (s *AntigravityGatewayService) Forward(ctx context.Context, c *gin.Context,
 		return nil, fmt.Errorf("获取 access_token 失败: %w", err)
 	}
 
-	// 获取 project_id
+	// 获取 project_id（部分账户类型可能没有）
 	projectID := strings.TrimSpace(account.GetCredential("project_id"))
-	if projectID == "" {
-		return nil, errors.New("project_id not found in credentials")
-	}
 
 	// 代理 URL
 	proxyURL := ""
@@ -368,26 +358,19 @@ func (s *AntigravityGatewayService) Forward(ctx context.Context, c *gin.Context,
 		return nil, fmt.Errorf("transform request: %w", err)
 	}
 
-	// 构建上游 URL
+	// 构建上游 action
 	action := "generateContent"
 	if claudeReq.Stream {
-		action = "streamGenerateContent"
-	}
-	fullURL := fmt.Sprintf("%s/v1internal:%s", antigravity.BaseURL, action)
-	if claudeReq.Stream {
-		fullURL += "?alt=sse"
+		action = "streamGenerateContent?alt=sse"
 	}
 
 	// 重试循环
 	var resp *http.Response
 	for attempt := 1; attempt <= antigravityMaxRetries; attempt++ {
-		upstreamReq, err := http.NewRequestWithContext(ctx, http.MethodPost, fullURL, bytes.NewReader(geminiBody))
+		upstreamReq, err := antigravity.NewAPIRequest(ctx, action, accessToken, geminiBody)
 		if err != nil {
 			return nil, err
 		}
-		upstreamReq.Header.Set("Content-Type", "application/json")
-		upstreamReq.Header.Set("Authorization", "Bearer "+accessToken)
-		upstreamReq.Header.Set("User-Agent", antigravity.UserAgent)
 
 		resp, err = s.httpUpstream.Do(upstreamReq, proxyURL)
 		if err != nil {
@@ -500,11 +483,8 @@ func (s *AntigravityGatewayService) ForwardGemini(ctx context.Context, c *gin.Co
 		return nil, fmt.Errorf("获取 access_token 失败: %w", err)
 	}
 
-	// 获取 project_id
+	// 获取 project_id（部分账户类型可能没有）
 	projectID := strings.TrimSpace(account.GetCredential("project_id"))
-	if projectID == "" {
-		return nil, errors.New("project_id not found in credentials")
-	}
 
 	// 代理 URL
 	proxyURL := ""
@@ -518,26 +498,22 @@ func (s *AntigravityGatewayService) ForwardGemini(ctx context.Context, c *gin.Co
 		return nil, err
 	}
 
-	// 构建上游 URL
+	// 构建上游 action
 	upstreamAction := action
 	if action == "generateContent" && stream {
 		upstreamAction = "streamGenerateContent"
 	}
-	fullURL := fmt.Sprintf("%s/v1internal:%s", antigravity.BaseURL, upstreamAction)
 	if stream || upstreamAction == "streamGenerateContent" {
-		fullURL += "?alt=sse"
+		upstreamAction += "?alt=sse"
 	}
 
 	// 重试循环
 	var resp *http.Response
 	for attempt := 1; attempt <= antigravityMaxRetries; attempt++ {
-		upstreamReq, err := http.NewRequestWithContext(ctx, http.MethodPost, fullURL, bytes.NewReader(wrappedBody))
+		upstreamReq, err := antigravity.NewAPIRequest(ctx, upstreamAction, accessToken, wrappedBody)
 		if err != nil {
 			return nil, err
 		}
-		upstreamReq.Header.Set("Content-Type", "application/json")
-		upstreamReq.Header.Set("Authorization", "Bearer "+accessToken)
-		upstreamReq.Header.Set("User-Agent", antigravity.UserAgent)
 
 		resp, err = s.httpUpstream.Do(upstreamReq, proxyURL)
 		if err != nil {

backend/internal/service/antigravity_oauth_service.go

@@ -141,7 +141,7 @@ func (s *AntigravityOAuthService) ExchangeCode(ctx context.Context, input *Antig
 		result.Email = userInfo.Email
 	}
 
-	// 获取 project_id
+	// 获取 project_id（部分账户类型可能没有）
 	loadResp, err := client.LoadCodeAssist(ctx, tokenResp.AccessToken)
 	if err != nil {
 		fmt.Printf("[AntigravityOAuth] 警告: 获取 project_id 失败: %v\n", err)

backend/internal/service/antigravity_quota_refresher.go

@@ -125,8 +125,8 @@ func (r *AntigravityQuotaRefresher) refreshAccountQuota(ctx context.Context, acc
 	accessToken := account.GetCredential("access_token")
 	projectID := account.GetCredential("project_id")
 
-	if accessToken == "" || projectID == "" {
-		return nil // 没有有效凭证，跳过
+	if accessToken == "" {
+		return nil // 没有 access_token，跳过
 	}
 
 	// token 过期则跳过，由 TokenRefreshService 负责刷新
@@ -151,7 +151,10 @@ func (r *AntigravityQuotaRefresher) refreshAccountQuota(ctx context.Context, acc
 		r.updateAccountTier(account, loadResp)
 	}
 
-	// 调用 API 获取配额
+	// 调用 API 获取配额（需要 projectID）
+	if projectID == "" {
+		return r.accountRepo.Update(ctx, account) // 没有 projectID，只更新 tier
+	}
 	modelsResp, err := client.FetchAvailableModels(ctx, accessToken, projectID)
 	if err != nil {
 		return err