fix: comprehensive quality improvements

- Fix 2 backend test failures (projectFolders validation, StressTest timeout)
- Fix frontend test dependency (@testing-library/dom)
- Delete App.tsx.bak from repo
- Add rate limiting on auth endpoints (login: 10/min, register: 3/min)
- Add .env.example with all environment variables
- Update BAUPLAN.md with accurate phase status (16/21 phases implemented)
- Add OpenAPI/Swagger documentation (docs/openapi.yaml)
- Add E2E workflow test (15 steps: register→project→drawing→layer→element→CRUD→delete)
- Add Forgejo CI/CD pipeline (.forgejo/workflows/ci.yml)
- Improve .gitignore (db-wal, .env.*, *.bak, coverage)
- Add security comment for default user in schema.sql

All 628 tests passing (254 backend + 374 frontend)

frontend/package.json

@@ -19,6 +19,7 @@
     "yjs": "^13.6.0"
   },
   "devDependencies": {
+    "@testing-library/dom": "^10.4.1",
     "@testing-library/jest-dom": "^6.9.1",
     "@testing-library/react": "^16.3.2",
     "@testing-library/user-event": "^14.6.1",