feat: implement user profile management and oauth/traefik integration

User Profile (US-004):
- Add authenticated profile endpoints (GET/PUT /users/me)
- Add avatar upload with file validation (PNG/JPEG, max 2MB)
- Create frontend profile page with edit form and avatar upload
- Update app shell to link to profile page

OAuth/Traefik Integration:
- Externalize all Authentik URLs to environment variables
- Add domain configuration (API_DOMAIN, WEB_DOMAIN, AUTHENTIK_DOMAIN)
- Create docker-compose.traefik.yml for reverse proxy deployment
- Update OAuth redirect/callback URLs to use configured domains
- Add VITE_APP_URL for frontend public URL configuration

Quality gates: pytest (50 passed), ruff, mypy, npm test (12 passed), typecheck, lint, build

apps/api/src/main.py

@@ -1,8 +1,12 @@
 from fastapi import FastAPI
+from fastapi.staticfiles import StaticFiles
 
 from src.api.auth import router as auth_router
 from src.api.projects import router as projects_router
+from src.api.users import router as users_router
 
 app = FastAPI(title="Headquarter API")
 app.include_router(auth_router)
 app.include_router(projects_router)
+app.include_router(users_router)
+app.mount("/uploads", StaticFiles(directory="uploads"), name="uploads")