feat(v2.1.2): align with ClawX schema + config-server port fallback

Three changes for v2.1.2:

1. bootstrap-xiapan now writes "agents.defaults.model.primary/fallbacks"
   (uclaw-cloud/deepseek-v4-flash + 3 fallbacks) and an empty models[],
   matching the ClawX commercial schema. Lets OpenClaw runtime auto-discover
   models from /v1/models instead of hard-coding a list that drifts.

2. config-server tries ports 18788..18798 with EADDRINUSE fallback and
   persists the live port to data/.openclaw/runtime.json so future tooling
   can discover it. Fixes silent failure when a second portable instance
   started while 18788 was occupied.

3. u-claw-app/package.json version 2.0.0 -> 2.1.2 so .exe/.dmg filenames
   align with the release tag.

u-claw-app/package.json

@@ -1,6 +1,6 @@
 {
   "name": "u-claw",
-  "version": "2.0.0",
+  "version": "2.1.2",
   "description": "U-Claw - AI 助手桌面版，插上 U 盘就能用",
   "main": "src/main.js",
   "author": "U-Claw <hello@u-claw.org> (https://u-claw.org)",