feat(frontend): 支持 Gemini OAuth 类型选择 (Code Assist/AI Studio)

- CreateAccountModal.vue: 新增 OAuth 类型选择 UI
- ReAuthAccountModal.vue: 重授权支持选择类型
- OAuthAuthorizationFlow.vue: 新增 Project ID 输入框
- AccountTestModal.vue: Gemini 模型默认选择优化
- useGeminiOAuth.ts: OAuth 逻辑参数变更
- gemini.ts: API 调用更新

frontend/src/api/admin/gemini.ts

@@ -12,16 +12,17 @@ export interface GeminiAuthUrlResponse {
 }
 
 export interface GeminiAuthUrlRequest {
-  redirect_uri: string
   proxy_id?: number
+  project_id?: string
+  oauth_type?: 'code_assist' | 'ai_studio'
 }
 
 export interface GeminiExchangeCodeRequest {
   session_id: string
   state: string
   code: string
-  redirect_uri: string
   proxy_id?: number
+  oauth_type?: 'code_assist' | 'ai_studio'
 }
 
 export type GeminiTokenInfo = Record<string, unknown>