feat: add VIP gating on cloud sync write endpoints + daily expiry reminder cron

- Add requireVip middleware to POST/PUT/DELETE /api/user-equity routes
- Extract sendExpiryReminders() from route handler for reuse
- Add node-cron job at 21:30 Asia/Shanghai daily for expiry reminders

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

package.json

@@ -20,23 +20,26 @@
   "author": "",
   "license": "MIT",
   "dependencies": {
-    "express": "^4.18.2",
-    "cors": "^2.8.5",
-    "helmet": "^7.1.0",
-    "morgan": "^1.10.0",
-    "dotenv": "^16.3.1",
-    "mongoose": "^8.0.3",
-    "jsonwebtoken": "^9.0.2",
-    "bcryptjs": "^2.4.3",
-    "express-validator": "^7.0.1",
     "axios": "^1.6.2",
-    "crypto-js": "^4.2.0"
+    "bcryptjs": "^2.4.3",
+    "cors": "^2.8.5",
+    "crypto-js": "^4.2.0",
+    "dotenv": "^16.3.1",
+    "express": "^4.18.2",
+    "express-validator": "^7.0.1",
+    "helmet": "^7.1.0",
+    "jsonwebtoken": "^9.0.2",
+    "mongoose": "^8.0.3",
+    "morgan": "^1.10.0",
+    "multer": "^1.4.4",
+    "node-cron": "^4.2.1",
+    "sharp": "^0.33.2"
   },
   "devDependencies": {
-    "nodemon": "^3.0.2",
-    "jest": "^29.7.0",
+    "@types/node": "^20.10.6",
     "eslint": "^8.56.0",
-    "@types/node": "^20.10.6"
+    "jest": "^29.7.0",
+    "nodemon": "^3.0.2"
   },
   "engines": {
     "node": ">=18.0.0"