feat(todo): add Prometheus metrics and update docs

- Add MetricsModule with prom-client for todo backend
- Add MetricsInterceptor for request tracking
- Update COMMANDS.md with presi and storage commands
- Update Grafana dashboards for backend monitoring

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docker/grafana/dashboards/backends.json

@@ -61,8 +61,8 @@
 			"targets": [
 				{
 					"datasource": { "type": "prometheus", "uid": "${datasource}" },
-					"expr": "rate(container_cpu_usage_seconds_total{name=~\".+\"}[5m]) * 100",
-					"legendFormat": "{{name}}",
+					"expr": "sum(rate(container_cpu_usage_seconds_total{id=~\"/docker/.+\"}[5m])) by (id) * 100",
+					"legendFormat": "{{id}}",
 					"refId": "A"
 				}
 			],
@@ -114,8 +114,8 @@
 			"targets": [
 				{
 					"datasource": { "type": "prometheus", "uid": "${datasource}" },
-					"expr": "container_memory_usage_bytes{name=~\".+\"}",
-					"legendFormat": "{{name}}",
+					"expr": "container_memory_usage_bytes{id=~\"/docker/.+\"}",
+					"legendFormat": "{{id}}",
 					"refId": "A"
 				}
 			],

docker/grafana/dashboards/system-overview.json

@@ -138,7 +138,7 @@
 			"targets": [
 				{
 					"datasource": { "type": "prometheus", "uid": "${datasource}" },
-					"expr": "(1 - (node_filesystem_avail_bytes{mountpoint=\"/\"} / node_filesystem_size_bytes{mountpoint=\"/\"})) * 100",
+					"expr": "(1 - (node_filesystem_avail_bytes{mountpoint=~\"/host_mnt/Users|/\"} / node_filesystem_size_bytes{mountpoint=~\"/host_mnt/Users|/\"})) * 100",
 					"refId": "A"
 				}
 			],
@@ -177,7 +177,7 @@
 			"targets": [
 				{
 					"datasource": { "type": "prometheus", "uid": "${datasource}" },
-					"expr": "count(container_last_seen{name=~\".+\"})",
+					"expr": "count(container_last_seen{id=~\"/docker/.+\"})",
 					"refId": "A"
 				}
 			],