feat(dependencies): add better-auth package to frontend and backend

apps/backend/package.json

@@ -11,6 +11,7 @@
     "prisma:migrate:deploy": "prisma migrate deploy"
   },
   "dependencies": {
+    "better-auth": "^1.6.11",
     "@noble/ciphers": "^2.1.1",
     "@personal-admin/common": "workspace:*",
     "@prisma/adapter-pg": "^7.8.0",

apps/frontend/package.json

@@ -9,6 +9,7 @@
     "preview": "vite preview"
   },
   "dependencies": {
+    "better-auth": "^1.6.11",
     "@hookform/resolvers": "^5.4.0",
     "@personal-admin/common": "workspace:*",
     "@tailwindcss/vite": "^4.3.0",