feat(search): global search aggregation backend (W9-G)

- GET /search?q=&scope=all|media|releases|actions&limit=: local works (title_alias
  exact/prefix/trgm + name prefix, slot status summary), TMDB candidates (cached,
  localEntityId), cross-site releases, page/action jump list; tookMs per group
- cross-site: enabled sites via shared per-site limiter, 15s AbortSignal timeout,
  site concurrency cap 4, same-query coalescing, 30s cache; partial + failedSites;
  results upserted to source_release; inventory overlay via GET /inventory
- GET /search/releases: site/resolution/source/size/free/H&R filters, sort, cursor,
  facets; shares the cache
- POST /search/releases/{siteId}/{siteReleaseId}/plan: forwards in-process to
  POST /acquisition-plans (same auth, validation, audit, rejections)
- contracts/search.ts, runbook, tests (partial/timeout, coalesce, cache, overlay,
  filters/sort, plan)

Co-Authored-By: Claude Opus 5.5 <[email protected]>

apps/server/test/modules.test.ts

@@ -43,7 +43,7 @@ const pingModule: ServerModule = {
 };
 
 describe("ServerModule 骨架", () => {
-  it("清单里是四个 W2 模块 + 文件管理 + Pi 上游 + 定时任务(末尾),名字唯一", () => {
+  it("清单里是四个 W2 模块 + 文件管理 + Pi 上游 + 定时任务 + 全局搜索(末尾),名字唯一", () => {
     expect(SERVER_MODULES.map((m) => m.name)).toEqual([
       "auth-settings",
       "sources-identity",
@@ -52,6 +52,7 @@ describe("ServerModule 骨架", () => {
       "file-manager",
       "pi",
       "schedules",
+      "search",
     ]);
   });