feat(observability): add Prometheus/Grafana/Loki/Alertmanager/Alloy stack and remove legacy Monitoring UI

backend/tests/test_observability.py

@@ -0,0 +1,37 @@
+"""Tests for observability metrics helpers."""
+
+import time
+
+from prometheus_client import REGISTRY
+
+from media_library_viewer_api.observability import record_backup_run
+
+
+def _metric_samples(metric_name):
+    return {
+        tuple(s.labels.values()): s.value
+        for family in REGISTRY.collect()
+        for s in family.samples
+        if s.name == metric_name
+    }
+
+
+def test_record_backup_run_increments_counter():
+    record_backup_run("job-a", "success", success=True)
+    record_backup_run("job-a", "failure")
+    record_backup_run("job-b", "success", success=True)
+
+    samples = _metric_samples("manage_backup_runs_total")
+    assert samples[("job-a", "success")] >= 1.0
+    assert samples[("job-a", "failure")] >= 1.0
+    assert samples[("job-b", "success")] >= 1.0
+
+
+def test_record_backup_run_sets_last_success_timestamp():
+    before = time.time()
+    record_backup_run("job-ts", "success", success=True)
+    after = time.time()
+
+    samples = _metric_samples("manage_backup_runs_last_success_timestamp")
+    value = samples[("job-ts",)]
+    assert before <= value <= after