Hub-and-Spoke Umbau: Multi-Tenant Zentrale + Satellite-Agent

- Backend: Customer/Satellite Models, customer_id auf Server/Job/Audit
- Satellite-API: heartbeat, poll (atomares Claiming), logs, result,
  scan-result, health-report - Auth via X-Api-Key (SHA-256 gehasht)
- Job-Queue: pending/claimed/running/success/failed + Stale-Janitor
- Batch-Trigger: ein Job pro Server, Satellite arbeitet sequenziell ab
- Credentials bleiben lokal: nur symbolische credential_ref zentral
- Neues Paket satellite/: Pull-Loop, WinRM/SSH/CAU/Scanner, PyInstaller-tauglich
- Frontend: Kunden-Switcher, Satelliten-View, Polling statt WebSocket
- Entfernt: WebSocket/Socket.io, Redis, zentrale Credentials, JobRunner
- Docs: README/AGENTS/PROMPT auf neue Architektur aktualisiert

backend/app/services/janitor.py

@@ -0,0 +1,47 @@
+"""Stale job janitor: marks claimed/running jobs as failed when their
+satellite stops reporting (e.g. satellite offline, job crashed).
+"""
+
+import asyncio
+from datetime import UTC, datetime, timedelta
+
+from sqlalchemy import select
+
+from app.core.config import get_settings
+from app.core.database import async_session_factory
+from app.core.logging import get_logger
+from app.models.update_job import JobStatus, UpdateJob
+
+settings = get_settings()
+logger = get_logger(__name__)
+
+CHECK_INTERVAL = 60  # seconds
+
+
+async def run_janitor() -> None:
+    """Background task; runs until cancelled."""
+    while True:
+        try:
+            await _sweep()
+        except Exception as exc:  # noqa: BLE001 - janitor must never die
+            logger.error("janitor.error", error=str(exc))
+        await asyncio.sleep(CHECK_INTERVAL)
+
+
+async def _sweep() -> None:
+    cutoff = datetime.now(UTC) - timedelta(seconds=settings.job_stale_timeout)
+    async with async_session_factory() as db:
+        result = await db.execute(
+            select(UpdateJob).where(
+                UpdateJob.status.in_([JobStatus.CLAIMED, JobStatus.RUNNING]),
+                UpdateJob.last_report_at < cutoff,
+            )
+        )
+        stale = list(result.scalars().all())
+        for job in stale:
+            job.status = JobStatus.FAILED
+            job.error = "Satellite meldet sich nicht mehr (Timeout)"
+            job.finished_at = datetime.now(UTC)
+            logger.warning("janitor.job_stale", job_id=job.id, satellite_id=job.satellite_id)
+        if stale:
+            await db.commit()