fix(examples): 全插件安全审查修复（qq/a2a/memo/calendar/rss/browser/bili/recoverydiag）

审查发现并修复 7 项问题：
- P1 qq: downloadURL 裸 http.Get 无超时 → 120s client
- P2 a2a: inbound http.Server 零超时 → Read 30s/Write 120s/Idle 60s
- P3 bili: output_dir 配置项零校验 → 系统目录黑名单（/、/etc、/usr、/var 等）
- P4 recoverydiag: db_path LLM 可控任意 sqlite → 强制限制 data 目录内
- P5 memo/calendar/rss: os.WriteFile 直写 → atomicWriteJSON (temp+rename)
- P6 qq: 3 处后台 goroutine（已读/rcon转发/下载）加 panic recover
- P7 browser: dump-dom failback Kill 后补 wait 回收僵尸进程

recoverydiag 此前被 .gitignore 排除，但其 db_path 安全修复
属生产代码，故取消忽略并入库。

全部经 plugindev 重打包升版安装验证 config_kept=true。

example/browser/plg.json

@@ -2,14 +2,20 @@
   "name": "browser",
   "name_zh": "浏览器",
   "name_en": "Browser",
-  "version": "2.0.0",
+  "version": "2.3.0",
   "description": "统一浏览器插件：搜索、HTTP抓取(quick)、无头渲染(normal)、交互式浏览器(interactive/CDP)",
   "author": "HomeAgent",
   "entry": "plugin.so",
-  "tags": ["web", "search", "fetch", "browser", "cdp"],
+  "tags": [
+    "web",
+    "search",
+    "fetch",
+    "browser",
+    "cdp"
+  ],
   "targets": "linux/amd64",
   "outdir": "dist",
   "bundle": true,
   "replaces": {},
   "source_dirs": []
-}
+}