feat: add Drizzle ORM support and update README with environment setup and migration scripts

Backend/README.md

@@ -1,15 +1,47 @@
 # backend
 
-To install dependencies:
+## Install
 
 ```bash
 bun install
 ```
 
-To run:
+## Environment
+
+Create a `.env` file:
 
 ```bash
-bun run index.ts
+cp .env.example .env
 ```
 
-This project was created using `bun init` in bun v1.3.5. [Bun](https://bun.com) is a fast all-in-one JavaScript runtime.
+Set:
+
+```bash
+DATABASE_URL=postgres://username:password@localhost:5432/database_name
+```
+
+## Run app
+
+```bash
+bun run dev
+```
+
+## Drizzle ORM
+
+Generate migrations:
+
+```bash
+bun run db:generate
+```
+
+Apply migrations:
+
+```bash
+bun run db:migrate
+```
+
+Open Drizzle Studio:
+
+```bash
+bun run db:studio
+```