test(gemini): 添加 Drive API 和 OAuth 服务单元测试

- 新增 drive_client_test.go：Drive API 客户端单元测试
- 新增 gemini_oauth_service_test.go：OAuth 服务单元测试
- 重构 account_handler.go：改进 RefreshTier API 实现
- 优化 drive_client.go：增强错误处理和重试逻辑
- 完善 repository 和 service 层：支持批量 tier 刷新
- 更新迁移文件编号：017 -> 024（避免冲突）

backend/internal/pkg/geminicli/drive_client.go

@@ -5,7 +5,9 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"math/rand"
 	"net/http"
+	"strconv"
 	"time"
 
 	"github.com/Wei-Shaw/sub2api/internal/pkg/httpclient"
@@ -49,13 +51,38 @@ func (c *driveClient) GetStorageQuota(ctx context.Context, accessToken, proxyURL
 		return nil, fmt.Errorf("failed to create HTTP client: %w", err)
 	}
 
-	// Retry logic with exponential backoff for rate limits
+	sleepWithContext := func(d time.Duration) error {
+		timer := time.NewTimer(d)
+		defer timer.Stop()
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		case <-timer.C:
+			return nil
+		}
+	}
+
+	// Retry logic with exponential backoff (+ jitter) for rate limits and transient failures
 	var resp *http.Response
 	maxRetries := 3
+	rng := rand.New(rand.NewSource(time.Now().UnixNano()))
 	for attempt := 0; attempt < maxRetries; attempt++ {
+		if ctx.Err() != nil {
+			return nil, fmt.Errorf("request cancelled: %w", ctx.Err())
+		}
+
 		resp, err = client.Do(req)
 		if err != nil {
-			return nil, fmt.Errorf("failed to execute request: %w", err)
+			// Network error retry
+			if attempt < maxRetries-1 {
+				backoff := time.Duration(1<<uint(attempt)) * time.Second
+				jitter := time.Duration(rng.Intn(1000)) * time.Millisecond
+				if err := sleepWithContext(backoff + jitter); err != nil {
+					return nil, fmt.Errorf("request cancelled: %w", err)
+				}
+				continue
+			}
+			return nil, fmt.Errorf("network error after %d attempts: %w", maxRetries, err)
 		}
 
 		// Success
@@ -63,18 +90,34 @@ func (c *driveClient) GetStorageQuota(ctx context.Context, accessToken, proxyURL
 			break
 		}
 
-		// Rate limit - retry with exponential backoff
-		if resp.StatusCode == http.StatusTooManyRequests && attempt < maxRetries-1 {
+		// Retry 429, 500, 502, 503 with exponential backoff + jitter
+		if (resp.StatusCode == http.StatusTooManyRequests ||
+			resp.StatusCode == http.StatusInternalServerError ||
+			resp.StatusCode == http.StatusBadGateway ||
+			resp.StatusCode == http.StatusServiceUnavailable) && attempt < maxRetries-1 {
 			_ = resp.Body.Close()
-			backoff := time.Duration(1<<uint(attempt)) * time.Second // 1s, 2s, 4s
-			time.Sleep(backoff)
+			backoff := time.Duration(1<<uint(attempt)) * time.Second
+			jitter := time.Duration(rng.Intn(1000)) * time.Millisecond
+			if err := sleepWithContext(backoff + jitter); err != nil {
+				return nil, fmt.Errorf("request cancelled: %w", err)
+			}
 			continue
 		}
 
-		// Other errors - return immediately
+		break
+	}
+
+	if resp == nil {
+		return nil, fmt.Errorf("request failed: no response received")
+	}
+
+	if resp.StatusCode != http.StatusOK {
 		body, _ := io.ReadAll(resp.Body)
 		_ = resp.Body.Close()
-		return nil, fmt.Errorf("drive API error (status %d): %s", resp.StatusCode, string(body))
+		// 记录完整错误
+		fmt.Printf("[DriveClient] API error (status %d): %s\n", resp.StatusCode, string(body))
+		// 只返回通用错误
+		return nil, fmt.Errorf("drive API error: status %d", resp.StatusCode)
 	}
 
 	defer func() { _ = resp.Body.Close() }()
@@ -94,10 +137,14 @@ func (c *driveClient) GetStorageQuota(ctx context.Context, accessToken, proxyURL
 	// Parse limit and usage (handle both string and number formats)
 	var limit, usage int64
 	if result.StorageQuota.Limit != "" {
-		_, _ = fmt.Sscanf(result.StorageQuota.Limit, "%d", &limit)
+		if val, err := strconv.ParseInt(result.StorageQuota.Limit, 10, 64); err == nil {
+			limit = val
+		}
 	}
 	if result.StorageQuota.Usage != "" {
-		_, _ = fmt.Sscanf(result.StorageQuota.Usage, "%d", &usage)
+		if val, err := strconv.ParseInt(result.StorageQuota.Usage, 10, 64); err == nil {
+			usage = val
+		}
 	}
 
 	return &DriveStorageInfo{

backend/internal/pkg/geminicli/drive_client_test.go

@@ -0,0 +1,19 @@
+package geminicli
+
+import "testing"
+
+func TestDriveStorageInfo(t *testing.T) {
+	// 测试 DriveStorageInfo 结构体
+	info := &DriveStorageInfo{
+		Limit: 100 * 1024 * 1024 * 1024, // 100GB
+		Usage: 50 * 1024 * 1024 * 1024,  // 50GB
+	}
+
+	if info.Limit != 100*1024*1024*1024 {
+		t.Errorf("Expected limit 100GB, got %d", info.Limit)
+	}
+	if info.Usage != 50*1024*1024*1024 {
+		t.Errorf("Expected usage 50GB, got %d", info.Usage)
+	}
+}
+