feat(emby): support multiple connection lines for remote mount (#9)

Add account-level multi-line configuration for emby_remote mounts.
Lines are stored in strm_accounts.config as a urls JSON array with
backward compatibility for the legacy single url field. The backend
automatically fails over to the next line on connection errors and
persists the working active_line index.

Frontend: multi-line editor on Emby mount page and STRM account dialog
with add/remove/reorder, line names, and URL validation.

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: truewhile <truewhile@users.noreply.github.com>

web/src/types/strm.ts

@@ -9,6 +9,11 @@ export const STRM_PROVIDER_LABELS: Record<StrmProvider, string> = {
   emby_remote: 'Emby 远程挂载',
 }
 
+export type EmbyRemoteLine = {
+  name: string
+  url: string
+}
+
 export interface StrmAccount {
   id: string
   name: string
@@ -23,6 +28,10 @@ export interface StrmAccount {
   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
+  /** 仅远程 Emby 挂载账号返回：多线路配置 */
+  emby_lines?: EmbyRemoteLine[]
+  /** 当前优先使用的线路下标 */
+  emby_active_line?: number
 }
 
 export interface StrmAccountInput {