feat: implement SSH key management

- Add backend API endpoints for SSH key CRUD (POST, GET, DELETE)
- Implement Ed25519 key generation with Fernet-encrypted private keys
- Add frontend SSH keys page with generate, list, and delete functionality
- Include copy-to-clipboard for public keys
- Add responsive CSS styles for key cards
- Register ssh_keys router in main.py
- Add basic auth tests for SSH key endpoints

Quality gates: ruff ✓, mypy ✓, typecheck ✓, lint ✓

apps/api/src/main.py

@@ -3,10 +3,12 @@ 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.ssh_keys import router as ssh_keys_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.include_router(ssh_keys_router)
 app.mount("/uploads", StaticFiles(directory="uploads"), name="uploads")