fix(release): 桌面版版本号跟 git tag 自动联动

之前 electron-builder 从 package.json 取版本号(写死 2.1.4),
导致 dmg/exe 文件名与 git tag(v2.1.5)脱节。

- 两个 electron build job 在构建前用 tag 号同步 package.json
  (npm version --no-git-tag-version),文件名自动跟 tag 走
- bump package.json 到 2.1.5 保持本地一致

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

u-claw-app/package.json

@@ -1,6 +1,6 @@
 {
   "name": "u-claw",
-  "version": "2.1.4",
+  "version": "2.1.5",
   "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)",