docs: add operational runbook, Grafana dashboard, and production docker-compose

Add comprehensive operational documentation:
- docs/operations/backup-restore.md: SQLCipher, file backend, blob backup/restore
- docs/operations/key-rotation.md: auth token, TLS, federation, DB key, OPAQUE rotation
- docs/operations/incident-response.md: playbook for common incidents
- docs/operations/scaling-guide.md: resource sizing, scaling triggers, capacity planning
- docs/operations/monitoring.md: Prometheus metrics, alert rules, log monitoring
- docs/operations/dashboards/qpq-overview.json: Grafana dashboard template
- docs/operations/prometheus.yml + alerts: Prometheus scrape and alert config
- docs/operations/grafana-provisioning/: auto-provisioning for datasources and dashboards
- docker-compose.prod.yml: production stack (server + Prometheus + Grafana)
- .env.example: documented environment variable template

docs/operations/grafana-provisioning/dashboards/default.yml

@@ -0,0 +1,12 @@
+apiVersion: 1
+
+providers:
+  - name: 'default'
+    orgId: 1
+    folder: 'quicproquo'
+    type: file
+    disableDeletion: false
+    editable: true
+    options:
+      path: /var/lib/grafana/dashboards
+      foldersFromFilesStructure: false

docs/operations/grafana-provisioning/datasources/prometheus.yml

@@ -0,0 +1,9 @@
+apiVersion: 1
+
+datasources:
+  - name: Prometheus
+    type: prometheus
+    access: proxy
+    url: http://prometheus:9090
+    isDefault: true
+    editable: false