Add embedded Express admin API and unified dev workflow.

Move admin backend into this repo (Express + MySQL on :8085) so npm run dev starts both API and Vite, with updated env defaults and Caddy config for gadm.tkmind.cn.

Co-authored-by: Cursor <cursoragent@cursor.com>

package.json

@@ -4,11 +4,15 @@
   "version": "0.1.0",
   "type": "module",
   "scripts": {
-    "dev": "vite",
+    "dev": "node scripts/dev.mjs",
+    "dev:web": "vite",
+    "dev:server": "node server/index.mjs",
     "build": "vite build",
     "preview": "vite preview"
   },
   "dependencies": {
+    "express": "^4.21.2",
+    "mysql2": "^3.22.5",
     "react": "^19.0.0",
     "react-dom": "^19.0.0",
     "react-router-dom": "^7.13.1"