feat: add PostgreSQL database support and development scripts

- Added pg and @types/pg dependencies for PostgreSQL integration
- Created database testing and backend initialization scripts
- Changed dev server port to 3002 to avoid conflicts

.env.example

@@ -0,0 +1,17 @@
+# Database Configuration
+DB_HOST=localhost
+DB_PORT=5432
+DB_NAME=repohub
+DB_USER=postgres
+DB_PASSWORD=your_password_here
+
+# Next.js Configuration
+NEXTAUTH_URL=http://localhost:3002
+NEXTAUTH_SECRET=your_secret_here
+
+# API Configuration
+API_BASE_URL=http://localhost:3000/api
+
+# Sync Configuration
+SYNC_ENABLED=true
+SYNC_INTERVAL=3600000 # 1 hour in milliseconds