fix: reschedule APScheduler job immediately when status check interval is updated

Interval was read once at startup — changing it via API had no effect
until server restart. Now calls reschedule_status_checks() after saving.

backend/app/api/routes/scan.py

@@ -8,6 +8,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.api.deps import get_current_user
 from app.core.config import settings
+from app.core.scheduler import reschedule_status_checks
 from app.db.database import AsyncSessionLocal, get_db
 from app.db.models import Node, PendingDevice, ScanRun
 from app.schemas.nodes import NodeCreate
@@ -110,6 +111,7 @@ async def update_scan_config(payload: ScanConfig, _: str = Depends(get_current_u
     try:
         settings.scanner_ranges = payload.ranges
         settings.save_overrides()
+        reschedule_status_checks(payload.interval_seconds)
         return payload
     except Exception as exc:
         raise HTTPException(status_code=500, detail=str(exc)) from exc

backend/app/core/scheduler.py

@@ -53,5 +53,11 @@ def start_scheduler() -> None:
     logger.info("Scheduler started — status checks every %ds", settings.status_checker_interval)
 
 
+def reschedule_status_checks(interval_seconds: int) -> None:
+    """Update the status check interval on the running scheduler."""
+    scheduler.reschedule_job("status_checks", trigger="interval", seconds=interval_seconds)
+    logger.info("Status checks rescheduled to every %ds", interval_seconds)
+
+
 def stop_scheduler() -> None:
     scheduler.shutdown(wait=False)

backend/tests/test_scan.py

@@ -156,6 +156,26 @@ async def test_ignore_device(client: AsyncClient, headers, pending_device):
     assert hidden_res.json() == []
 
 
+# --- Scan config ---
+
+@pytest.mark.asyncio
+async def test_update_scan_config_reschedules_interval(client: AsyncClient, headers):
+    """Saving a new interval must reschedule the running APScheduler job immediately."""
+    with (
+        patch("app.api.routes.scan.settings") as mock_settings,
+        patch("app.api.routes.scan.reschedule_status_checks") as mock_reschedule,
+    ):
+        mock_settings.scanner_ranges = []
+        mock_settings.save_overrides = lambda: None
+        res = await client.post(
+            "/api/v1/scan/config",
+            json={"ranges": ["192.168.1.0/24"], "interval_seconds": 30},
+            headers=headers,
+        )
+    assert res.status_code == 200
+    mock_reschedule.assert_called_once_with(30)
+
+
 # --- Scan runs ---
 
 @pytest.mark.asyncio