Add user auth with JWT, switch to bun test

- User table with company_id FK, unique email, role enum
- Register/login routes with bcrypt + JWT token generation
- Auth plugin with authenticate decorator and role guards
- Login uses globally unique email (no company header needed)
- Dev-auth plugin kept as fallback when JWT_SECRET not set
- Switched from vitest to bun:test (vitest had ESM resolution
  issues with zod in Bun's module structure)
- Upgraded to zod 4
- Added Dockerfile.dev and API service to docker-compose
- 8 tests passing (health + auth)

packages/backend/src/plugins/database.ts

@@ -1,7 +1,10 @@
 import fp from 'fastify-plugin'
 import { drizzle } from 'drizzle-orm/postgres-js'
 import postgres from 'postgres'
-import * as schema from '../db/schema/stores.js'
+import * as storeSchema from '../db/schema/stores.js'
+import * as userSchema from '../db/schema/users.js'
+
+const schema = { ...storeSchema, ...userSchema }
 
 declare module 'fastify' {
   interface FastifyInstance {