feat(handler): 添加 Gemini OAuth Handler 和完善依赖注入

- 新增 Gemini OAuth 授权处理器
- 扩展账号和网关处理器支持 Gemini
- 注册 Gemini 相关路由
- 更新 Wire 依赖注入配置（所有层）
- 更新 Docker Compose 配置

backend/internal/handler/admin/account_handler.go

@@ -30,6 +30,7 @@ type AccountHandler struct {
 	adminService        service.AdminService
 	oauthService        *service.OAuthService
 	openaiOAuthService  *service.OpenAIOAuthService
+	geminiOAuthService  *service.GeminiOAuthService
 	rateLimitService    *service.RateLimitService
 	accountUsageService *service.AccountUsageService
 	accountTestService  *service.AccountTestService
@@ -42,6 +43,7 @@ func NewAccountHandler(
 	adminService service.AdminService,
 	oauthService *service.OAuthService,
 	openaiOAuthService *service.OpenAIOAuthService,
+	geminiOAuthService *service.GeminiOAuthService,
 	rateLimitService *service.RateLimitService,
 	accountUsageService *service.AccountUsageService,
 	accountTestService *service.AccountTestService,
@@ -52,6 +54,7 @@ func NewAccountHandler(
 		adminService:        adminService,
 		oauthService:        oauthService,
 		openaiOAuthService:  openaiOAuthService,
+		geminiOAuthService:  geminiOAuthService,
 		rateLimitService:    rateLimitService,
 		accountUsageService: accountUsageService,
 		accountTestService:  accountTestService,
@@ -345,6 +348,19 @@ func (h *AccountHandler) Refresh(c *gin.Context) {
 				newCredentials[k] = v
 			}
 		}
+	} else if account.Platform == model.PlatformGemini {
+		tokenInfo, err := h.geminiOAuthService.RefreshAccountToken(c.Request.Context(), account)
+		if err != nil {
+			response.InternalError(c, "Failed to refresh credentials: "+err.Error())
+			return
+		}
+
+		newCredentials = h.geminiOAuthService.BuildAccountCredentials(tokenInfo)
+		for k, v := range account.Credentials {
+			if _, exists := newCredentials[k]; !exists {
+				newCredentials[k] = v
+			}
+		}
 	} else {
 		// Use Anthropic/Claude OAuth service to refresh token
 		tokenInfo, err := h.oauthService.RefreshAccountToken(c.Request.Context(), account)

backend/internal/handler/admin/gemini_oauth_handler.go

@@ -0,0 +1,71 @@
+package admin
+
+import (
+	"github.com/Wei-Shaw/sub2api/internal/pkg/response"
+	"github.com/Wei-Shaw/sub2api/internal/service"
+
+	"github.com/gin-gonic/gin"
+)
+
+type GeminiOAuthHandler struct {
+	geminiOAuthService *service.GeminiOAuthService
+}
+
+func NewGeminiOAuthHandler(geminiOAuthService *service.GeminiOAuthService) *GeminiOAuthHandler {
+	return &GeminiOAuthHandler{geminiOAuthService: geminiOAuthService}
+}
+
+type GeminiGenerateAuthURLRequest struct {
+	ProxyID     *int64 `json:"proxy_id"`
+	RedirectURI string `json:"redirect_uri" binding:"required"`
+}
+
+// GenerateAuthURL generates Google OAuth authorization URL for Gemini.
+// POST /api/v1/admin/gemini/oauth/auth-url
+func (h *GeminiOAuthHandler) GenerateAuthURL(c *gin.Context) {
+	var req GeminiGenerateAuthURLRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		response.BadRequest(c, "Invalid request: "+err.Error())
+		return
+	}
+
+	result, err := h.geminiOAuthService.GenerateAuthURL(c.Request.Context(), req.ProxyID, req.RedirectURI)
+	if err != nil {
+		response.InternalError(c, "Failed to generate auth URL: "+err.Error())
+		return
+	}
+
+	response.Success(c, result)
+}
+
+type GeminiExchangeCodeRequest struct {
+	SessionID   string `json:"session_id" binding:"required"`
+	State       string `json:"state" binding:"required"`
+	Code        string `json:"code" binding:"required"`
+	RedirectURI string `json:"redirect_uri" binding:"required"`
+	ProxyID     *int64 `json:"proxy_id"`
+}
+
+// ExchangeCode exchanges authorization code for tokens.
+// POST /api/v1/admin/gemini/oauth/exchange-code
+func (h *GeminiOAuthHandler) ExchangeCode(c *gin.Context) {
+	var req GeminiExchangeCodeRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		response.BadRequest(c, "Invalid request: "+err.Error())
+		return
+	}
+
+	tokenInfo, err := h.geminiOAuthService.ExchangeCode(c.Request.Context(), &service.GeminiExchangeCodeInput{
+		SessionID:   req.SessionID,
+		State:       req.State,
+		Code:        req.Code,
+		RedirectURI: req.RedirectURI,
+		ProxyID:     req.ProxyID,
+	})
+	if err != nil {
+		response.BadRequest(c, "Failed to exchange code: "+err.Error())
+		return
+	}
+
+	response.Success(c, tokenInfo)
+}