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)

package.json

@@ -16,5 +16,8 @@
     "eslint": "^9",
     "typescript": "^5",
     "typescript-eslint": "^8"
+  },
+  "dependencies": {
+    "zod": "^4.3.6"
   }
 }