feat(gemini): 优化 OAuth 和配额展示

主要改进：
- 修复 google_one OAuth scopes 配置问题
- 添加 Gemini 账号配额展示组件
- 优化 Code Assist 类型检测逻辑
- 添加 OAuth 测试用例

frontend/src/api/admin/gemini.ts

@@ -19,7 +19,7 @@ export interface GeminiOAuthCapabilities {
 export interface GeminiAuthUrlRequest {
   proxy_id?: number
   project_id?: string
-  oauth_type?: 'code_assist' | 'ai_studio'
+  oauth_type?: 'code_assist' | 'google_one' | 'ai_studio'
 }
 
 export interface GeminiExchangeCodeRequest {
@@ -27,10 +27,22 @@ export interface GeminiExchangeCodeRequest {
   state: string
   code: string
   proxy_id?: number
-  oauth_type?: 'code_assist' | 'ai_studio'
+  oauth_type?: 'code_assist' | 'google_one' | 'ai_studio'
 }
 
-export type GeminiTokenInfo = Record<string, unknown>
+export type GeminiTokenInfo = {
+  access_token?: string
+  refresh_token?: string
+  token_type?: string
+  scope?: string
+  expires_in?: number
+  expires_at?: number
+  project_id?: string
+  oauth_type?: string
+  tier_id?: string
+  extra?: Record<string, unknown>
+  [key: string]: unknown
+}
 
 export async function generateAuthUrl(
   payload: GeminiAuthUrlRequest