feat: add backup alert background poller

backend/tests/test_backups.py

@@ -1,5 +1,6 @@
 import tempfile
 from pathlib import Path
+
 from media_library_viewer_api.services.settings_store import SettingsStore
 
 
@@ -9,7 +10,9 @@ def test_backup_schema_created():
         store = SettingsStore(db_path)
         store.init_schema()
         with store.connect() as conn:
-            tables = conn.execute("SELECT name FROM sqlite_master WHERE type='table' AND name LIKE 'backup_%'").fetchall()
+            tables = conn.execute(
+                "SELECT name FROM sqlite_master WHERE type='table' AND name LIKE 'backup_%'"
+            ).fetchall()
             table_names = [t[0] for t in tables]
             assert "backup_jobs" in table_names
             assert "backup_runs" in table_names
@@ -72,3 +75,34 @@ def test_alert_failed_status():
     assert len(alerts) == 1
     assert alerts[0]["alert_type"] == "failed_status"
     assert alerts[0]["severity"] == "critical"
+
+
+def test_backup_poller_detects_missed_schedule():
+    import tempfile
+    from pathlib import Path
+
+    from media_library_viewer_api.services.backup_poller import BackupAlertPoller
+    from media_library_viewer_api.services.settings_store import SettingsStore
+
+    with tempfile.TemporaryDirectory() as tmpdir:
+        db_path = Path(tmpdir) / "test_settings.sqlite"
+        store = SettingsStore(db_path)
+        store.init_schema()
+
+        import time
+        # Create job with created_at in the past so it's already overdue
+        past_time = int(time.time()) - 200
+        job = store.upsert_backup_job({
+            "name": "old-job",
+            "schedule_interval_seconds": 60,
+        })
+        # Override created_at to be in the past so missed schedule fires
+        with store.connect() as conn:
+            conn.execute("UPDATE backup_jobs SET created_at = ? WHERE id = ?", (past_time, job["id"]))
+
+        poller = BackupAlertPoller()
+        poller._run_cycle(store)
+
+        alerts = store.list_backup_alerts(job_id=job["id"])
+        assert len(alerts) == 1
+        assert alerts[0]["alert_type"] == "missed_schedule"