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)

CLAUDE.md

@@ -14,7 +14,7 @@
 - **Queue:** BullMQ (Valkey-backed)
 - **Cache:** Valkey 8 (Redis-compatible fork)
 - **Monorepo:** Turborepo with Bun workspaces
-- **Testing:** Vitest
+- **Testing:** bun test (built-in, uses bun:test imports)
 - **Linting:** ESLint 9 flat config + Prettier
 
 ## Package Namespace