Add Drizzle ORM setup and database configuration

- Add drizzle.config.ts for database migrations
- Create server/database/ structure with schema
- Add drizzle-orm and postgres dependencies
- Add db:* npm scripts for database management

drizzle.config.ts

@@ -0,0 +1,10 @@
+import { defineConfig } from 'drizzle-kit'
+
+export default defineConfig({
+  schema: './server/database/schema.ts',
+  out: './server/database/migrations',
+  dialect: 'postgresql',
+  dbCredentials: {
+    url: process.env.DATABASE_URL!,
+  },
+})