fix: Emby 远程挂载账号编辑保留凭据 + 代理开关回显

- UpdateStrmAccount 对 emby_remote 做合并式更新：只覆盖传入键，未提及的
  地址/用户名/密码/token 密文保留，避免编辑代理开关时清空凭据
- 账号列表/编辑表单回显 proxy_play（服务端解密后下发）
- 前端 StrmAccount 类型与编辑对话框支持 proxy_play 回显

web/src/pages/StrmDialogs.tsx

@@ -111,7 +111,7 @@ export function StrmAccountDialog({
   const [username, setUsername] = useState('')
   const [password, setPassword] = useState('')
   const [token, setToken] = useState('')
-  const [proxyPlay, setProxyPlay] = useState(false)
+  const [proxyPlay, setProxyPlay] = useState(existing?.proxy_play ?? false)
   const [saving, setSaving] = useState(false)
 
   const buildConfig = (): Record<string, string> => {

web/src/types/strm.ts

@@ -21,6 +21,8 @@ export interface StrmAccount {
   last_test_ok: boolean
   has_credential: boolean
   provider_label: string
+  /** 仅远程 Emby 挂载账号返回：播放流量是否经过 MMTL 代理 */
+  proxy_play?: boolean
 }
 
 export interface StrmAccountInput {