feat: add independent dashboard health endpoint (#26)

src/main.py

@@ -21,6 +21,12 @@ app.add_middleware(
 app.include_router(frontend_router)
 
 
+@app.get("/healthz")
+def health() -> dict[str, str]:
+    """Return process liveness without depending on Gitea."""
+    return {"status": "ok", "service": "stackchain-dashboard"}
+
+
 @app.get("/api/v1/context")
 async def context() -> JSONResponse:
     try: