chore(db): migrate from SQLite to PostgreSQL

- Change Prisma provider from sqlite to postgresql
- Replace better-sqlite3 adapter with @prisma/adapter-pg
- Update prisma.config.ts and lib/prisma.ts for PostgreSQL
- Add DATABASE_URL to .env.local
- Regenerate Prisma client for PostgreSQL
- Recreate migrations for PostgreSQL database

package.json

@@ -13,24 +13,24 @@
   },
   "dependencies": {
     "@panva/hkdf": "^1.2.1",
+    "@prisma/adapter-pg": "^7.7.0",
     "@prisma/client": "^7.7.0",
     "bcryptjs": "^3.0.3",
     "jose": "^6.2.2",
     "next": "16.2.3",
     "next-auth": "5.0.0-beta.30",
+    "pg": "^8.20.0",
     "react": "19.2.4",
     "react-dom": "19.2.4",
     "simple-icons": "^16.15.0"
   },
   "devDependencies": {
-    "@prisma/adapter-better-sqlite3": "^7.7.0",
     "@tailwindcss/postcss": "^4",
     "@types/bcryptjs": "^3.0.0",
     "@types/better-sqlite3": "^7.6.13",
     "@types/node": "^20",
     "@types/react": "^19",
     "@types/react-dom": "^19",
-    "better-sqlite3": "12",
     "eslint": "^9",
     "eslint-config-next": "16.2.3",
     "prisma": "7",