merge: 合并 upstream/main 并解决冲突

解决了以下文件的冲突：
- backend/internal/handler/admin/setting_handler.go
  - 采用 upstream 的字段对齐风格和 *Configured 字段名
  - 添加 EnableIdentityPatch 和 IdentityPatchPrompt 字段

- backend/internal/handler/gateway_handler.go
  - 采用 upstream 的 billingErrorDetails 错误处理方式

- frontend/src/api/admin/settings.ts
  - 采用 upstream 的 *_configured 字段名
  - 添加 enable_identity_patch 和 identity_patch_prompt 字段

- frontend/src/views/admin/SettingsView.vue
  - 合并 turnstile_secret_key_configured 字段
  - 保留 enable_identity_patch 和 identity_patch_prompt 字段

frontend/src/api/admin/settings.ts

@@ -26,20 +26,44 @@ export interface SystemSettings {
   smtp_host: string
   smtp_port: number
   smtp_username: string
-  smtp_password: string
+  smtp_password_configured: boolean
   smtp_from_email: string
   smtp_from_name: string
   smtp_use_tls: boolean
   // Cloudflare Turnstile settings
   turnstile_enabled: boolean
   turnstile_site_key: string
-  turnstile_secret_key: string
-
+  turnstile_secret_key_configured: boolean
   // Identity patch configuration (Claude -> Gemini)
   enable_identity_patch: boolean
   identity_patch_prompt: string
 }
 
+export interface UpdateSettingsRequest {
+  registration_enabled?: boolean
+  email_verify_enabled?: boolean
+  default_balance?: number
+  default_concurrency?: number
+  site_name?: string
+  site_logo?: string
+  site_subtitle?: string
+  api_base_url?: string
+  contact_info?: string
+  doc_url?: string
+  smtp_host?: string
+  smtp_port?: number
+  smtp_username?: string
+  smtp_password?: string
+  smtp_from_email?: string
+  smtp_from_name?: string
+  smtp_use_tls?: boolean
+  turnstile_enabled?: boolean
+  turnstile_site_key?: string
+  turnstile_secret_key?: string
+  enable_identity_patch?: boolean
+  identity_patch_prompt?: string
+}
+
 /**
  * Get all system settings
  * @returns System settings
@@ -54,7 +78,7 @@ export async function getSettings(): Promise<SystemSettings> {
  * @param settings - Partial settings to update
  * @returns Updated settings
  */
-export async function updateSettings(settings: Partial<SystemSettings>): Promise<SystemSettings> {
+export async function updateSettings(settings: UpdateSettingsRequest): Promise<SystemSettings> {
   const { data } = await apiClient.put<SystemSettings>('/admin/settings', settings)
   return data
 }