feat(backend): 添加 Gemini V1beta Handler 和路由

- 新增 gemini_v1beta_handler.go: 代理原生 Google API 格式
- 更新 gemini_oauth_handler.go: 移除 redirectUri，新增 oauthType
- 更新 account_handler.go: 账户 Handler 增强
- 更新 router.go: 注册 v1beta 路由
- 更新 config.go: Gemini OAuth 通过环境变量配置
- 更新 wire_gen.go: 依赖注入

backend/internal/handler/admin/gemini_oauth_handler.go

@@ -1,6 +1,10 @@
 package admin
 
 import (
+	"fmt"
+	"strings"
+
+	"github.com/Wei-Shaw/sub2api/internal/pkg/geminicli"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/response"
 	"github.com/Wei-Shaw/sub2api/internal/service"
 
@@ -16,8 +20,11 @@ func NewGeminiOAuthHandler(geminiOAuthService *service.GeminiOAuthService) *Gemi
 }
 
 type GeminiGenerateAuthURLRequest struct {
-	ProxyID     *int64 `json:"proxy_id"`
-	RedirectURI string `json:"redirect_uri" binding:"required"`
+	ProxyID   *int64 `json:"proxy_id"`
+	ProjectID string `json:"project_id"`
+	// OAuth 类型: "code_assist" (需要 project_id) 或 "ai_studio" (不需要 project_id)
+	// 默认为 "code_assist" 以保持向后兼容
+	OAuthType string `json:"oauth_type"`
 }
 
 // GenerateAuthURL generates Google OAuth authorization URL for Gemini.
@@ -29,9 +36,31 @@ func (h *GeminiOAuthHandler) GenerateAuthURL(c *gin.Context) {
 		return
 	}
 
-	result, err := h.geminiOAuthService.GenerateAuthURL(c.Request.Context(), req.ProxyID, req.RedirectURI)
+	// 默认使用 code_assist 以保持向后兼容
+	oauthType := strings.TrimSpace(req.OAuthType)
+	if oauthType == "" {
+		oauthType = "code_assist"
+	}
+	if oauthType != "code_assist" && oauthType != "ai_studio" {
+		response.BadRequest(c, "Invalid oauth_type: must be 'code_assist' or 'ai_studio'")
+		return
+	}
+
+	redirectURI := deriveGeminiRedirectURI(c)
+	if oauthType == "ai_studio" {
+		// AI Studio OAuth uses a localhost redirect URI to support the "copy/paste callback URL"
+		// flow (no server-side callback endpoint needed).
+		redirectURI = geminicli.AIStudioOAuthRedirectURI
+	}
+	result, err := h.geminiOAuthService.GenerateAuthURL(c.Request.Context(), req.ProxyID, redirectURI, req.ProjectID, oauthType)
 	if err != nil {
-		response.InternalError(c, "Failed to generate auth URL: "+err.Error())
+		msg := err.Error()
+		// Treat missing/invalid OAuth client configuration as a user/config error.
+		if strings.Contains(msg, "OAuth client not configured") || strings.Contains(msg, "requires your own OAuth Client") {
+			response.BadRequest(c, "Failed to generate auth URL: "+msg)
+			return
+		}
+		response.InternalError(c, "Failed to generate auth URL: "+msg)
 		return
 	}
 
@@ -39,11 +68,12 @@ func (h *GeminiOAuthHandler) GenerateAuthURL(c *gin.Context) {
 }
 
 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"`
+	SessionID string `json:"session_id" binding:"required"`
+	State     string `json:"state" binding:"required"`
+	Code      string `json:"code" binding:"required"`
+	ProxyID   *int64 `json:"proxy_id"`
+	// OAuth 类型: "code_assist" 或 "ai_studio"，需要与 GenerateAuthURL 时的类型一致
+	OAuthType string `json:"oauth_type"`
 }
 
 // ExchangeCode exchanges authorization code for tokens.
@@ -55,12 +85,22 @@ func (h *GeminiOAuthHandler) ExchangeCode(c *gin.Context) {
 		return
 	}
 
+	// 默认使用 code_assist 以保持向后兼容
+	oauthType := strings.TrimSpace(req.OAuthType)
+	if oauthType == "" {
+		oauthType = "code_assist"
+	}
+	if oauthType != "code_assist" && oauthType != "ai_studio" {
+		response.BadRequest(c, "Invalid oauth_type: must be 'code_assist' or 'ai_studio'")
+		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,
+		SessionID: req.SessionID,
+		State:     req.State,
+		Code:      req.Code,
+		ProxyID:   req.ProxyID,
+		OAuthType: oauthType,
 	})
 	if err != nil {
 		response.BadRequest(c, "Failed to exchange code: "+err.Error())
@@ -69,3 +109,25 @@ func (h *GeminiOAuthHandler) ExchangeCode(c *gin.Context) {
 
 	response.Success(c, tokenInfo)
 }
+
+func deriveGeminiRedirectURI(c *gin.Context) string {
+	origin := strings.TrimSpace(c.GetHeader("Origin"))
+	if origin != "" {
+		return strings.TrimRight(origin, "/") + "/auth/callback"
+	}
+
+	scheme := "http"
+	if c.Request.TLS != nil {
+		scheme = "https"
+	}
+	if xfProto := strings.TrimSpace(c.GetHeader("X-Forwarded-Proto")); xfProto != "" {
+		scheme = strings.TrimSpace(strings.Split(xfProto, ",")[0])
+	}
+
+	host := strings.TrimSpace(c.Request.Host)
+	if xfHost := strings.TrimSpace(c.GetHeader("X-Forwarded-Host")); xfHost != "" {
+		host = strings.TrimSpace(strings.Split(xfHost, ",")[0])
+	}
+
+	return fmt.Sprintf("%s://%s/auth/callback", scheme, host)
+}