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

drizzle.config.ts

@@ -0,0 +1,10 @@
+import { defineConfig } from "drizzle-kit"
+
+export default defineConfig({
+  schema: "./lib/db/schema/",
+  out: "./drizzle/",
+  dialect: "postgresql",
+  dbCredentials: {
+    url: process.env.DATABASE_URL!,
+  },
+})