feat(01-01): install Drizzle ORM, postgres-js, and configure DB client

- drizzle-orm@0.45.2 + postgres@3.4.9 installed (postgres-js driver)
- drizzle-kit@0.31.10 installed as dev dependency
- nanoid@5, zod@4, react-hook-form, @hookform/resolvers installed
- src/db/index.ts: Drizzle client initialized with postgres-js driver
- drizzle.config.ts: configured for postgresql dialect + src/db/schema.ts
- .env.example: added as public template (no secrets)
- .gitignore: allow .env.example while blocking all other .env* files

drizzle.config.ts

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