feat(subtitles): connect M-Team search and download to online workflow

通过既有provider表复用M-Team站点适配器的凭据、UA和共享限流；搜索只返回稳定字幕ID，下载签名现场获取，沿用沙箱解析、写入历史与撤销。迁移0096扩展字幕来源，schema反射同步。独立测试库验证M-Team真实API形状与旧字幕来源。参考：MoviePilot v3.2.4 app/modules/indexer/spider/mtorrent.py。

packages/db/migrations/0096_mteam_subtitles.ts

@@ -0,0 +1,22 @@
+import type { Kysely } from "kysely";
+import { execDdl, oneOf } from "../src/migration-helpers.ts";
+
+// M-Team 字幕沿用字幕资产与可撤销历史，只扩展来源，不保存下载签名。
+// biome-ignore lint/suspicious/noExplicitAny: 迁移不依赖应用表类型
+export async function up(db: Kysely<any>): Promise<void> {
+  await execDdl(
+    db,
+    `alter table subtitle_write drop constraint subtitle_write_source_check;
+     alter table subtitle_write add constraint subtitle_write_source_check ${oneOf("source", ["upload", "subhd", "zimuku", "mteam"])};`,
+  );
+}
+
+// biome-ignore lint/suspicious/noExplicitAny: 同上
+export async function down(db: Kysely<any>): Promise<void> {
+  // 有新来源的历史时拒绝回退，不删除记录或改写其来源。
+  await execDdl(
+    db,
+    `alter table subtitle_write drop constraint subtitle_write_source_check;
+     alter table subtitle_write add constraint subtitle_write_source_check ${oneOf("source", ["upload", "subhd", "zimuku"])};`,
+  );
+}