k8s/monitoring: add prometheus grafana loki observability

- Loki log aggregation (MinIO backed, 10-day retention)
- Promtail daemonset (pod + talos journal logs)
- Prometheus + kube-state-metrics
- Grafana dashboards (6-row template per service)

k8s/monitoring/alerts/svc-story-crater-frontend-rules.yaml

@@ -0,0 +1,33 @@
+apiVersion: monitoring.coreos.com/v1
+kind: PrometheusRule
+metadata:
+  name: story-crater-frontend-rules
+  namespace: story-crater-frontend
+spec:
+  groups:
+    - name: story-crater-frontend.rules
+      interval: 15s
+      rules:
+        - alert: StoryCraterFrontendHighErrorRate
+          expr: |
+            (
+              sum(rate(story_crater_frontend_http_requests_total{status=~"5.."}[5m]))
+              /
+              sum(rate(story_crater_frontend_http_requests_total[5m]))
+            ) > 0.05
+          for: 10m
+          labels:
+            severity: warning
+          annotations:
+            summary: "High error rate on story-crater-frontend"
+            description: "5xx error rate exceeded 5% of total requests for 10 minutes. Value: {{ $value | humanizePercentage }}"
+
+        - alert: StoryCraterFrontendWebVitalsLCPRegression
+          expr: |
+            histogram_quantile(0.75, story_crater_frontend_web_vitals_lcp_ms) > 2500
+          for: 10m
+          labels:
+            severity: warning
+          annotations:
+            summary: "LCP (Largest Contentful Paint) regression on story-crater-frontend"
+            description: "LCP p75 exceeded 2500ms for 10 minutes. Value: {{ $value }}ms"