feat(db): setup drizzle config, client and package scripts

- Add drizzle.config.ts with PostgreSQL dialect configuration
- Create lib/db/index.ts with Drizzle ORM client and pg Pool
- Add db:generate, db:migrate, db:studio, db:push scripts to package.json

Part of Chunk 1: Drizzle Config & DB Client setup

lib/db/index.ts

@@ -0,0 +1,9 @@
+import { drizzle } from "drizzle-orm/node-postgres"
+import { Pool } from "pg"
+import * as schema from "./schema"
+
+const pool = new Pool({
+  connectionString: process.env.DATABASE_URL,
+})
+
+export const db = drizzle(pool, { schema })