Scaffold backend (FastAPI/uv) and frontend (SvelteKit/bun)

Backend: FastAPI app with health check, AppError hierarchy, stderr
logging via LOG_LEVEL, ruff+pyright(strict) config, pytest passing.

Frontend: SvelteKit (TS) with prettier, eslint, vitest (unit +
component), adapter-node for self-hosted deployment on Zeus.

Co-Authored-By: Claude <noreply@anthropic.com>

backend/tests/test_health.py

@@ -0,0 +1,11 @@
+from fastapi.testclient import TestClient
+
+from app.main import app
+
+client = TestClient(app)
+
+
+def test_health() -> None:
+    response = client.get("/health")
+    assert response.status_code == 200
+    assert response.json() == {"status": "ok"}