feat(server): browser module with DB-backed sessions, takeover lease and browser.* capabilities

/browser/providers, /browser/sessions (open/close/list), navigate/snapshot/screenshot/
click/type/scroll/select/extract/download and control acquire/release. Human input
needs an active lease; expiry or captcha moves the session to waiting with a decision;
release forces a fresh snapshot. Downloads are staged under DATA_DIR/tmp, verified by
infohash and submitted through POST /acquisition-plans. Capability count 21 -> 25.

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 + 全局搜索 + 进程与健康(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 + 浏览器 + 进程与健康(末尾),名字唯一", () => {
     expect(SERVER_MODULES.map((m) => m.name)).toEqual([
       "auth-settings",
       "sources-identity",
@@ -53,6 +53,7 @@ describe("ServerModule 骨架", () => {
       "pi",
       "schedules",
       "search",
+      "browser",
       "system",
     ]);
   });