fix(otel): lazy-init metrics and fix Grafana dashboards

- Fix OTel custom metrics not reaching Prometheus: ESM static import
  hoisting caused metrics.getMeter() to run before sdk.start(), getting
  NoopMeterProvider. Changed to lazy-init pattern so instruments are
  created on first use after the SDK configures the real MeterProvider.

- Fix Grafana dashboards job labels: OTel adds service.namespace prefix
  (job=farmafinder/farmafinder-backend), updated queries to use regex
  match (job=~".*farmafinder-backend").

- Fix histogram metric names: OTel appends unit suffix (_milliseconds)
  to histogram names (e.g. http_request_duration_ms_milliseconds_bucket).

Verified: app_heartbeat_total, http_requests_total, db_query_duration_ms,
redis_cmd_duration_ms, and all other custom metrics now flow correctly
through OTLP -> Alloy -> Prometheus remote_write.

monitoring/dashboards/farmafinder-overview.json

@@ -11,20 +11,20 @@
       "id": 1, "title": "Backend req/s", "type": "stat",
       "gridPos": { "h": 5, "w": 6, "x": 0, "y": 0 },
       "datasource": { "type": "prometheus", "uid": "PBFA97CFB590B2093" },
-      "targets": [ { "expr": "sum(rate(http_requests_total{job=\"farmafinder-backend\"}[5m]))", "legendFormat": "req/s" } ]
+      "targets": [ { "expr": "sum(rate(http_requests_total{job=~\".*farmafinder-backend\"}[5m]))", "legendFormat": "req/s" } ]
     },
     {
       "id": 2, "title": "Backend 5xx ratio", "type": "stat",
       "gridPos": { "h": 5, "w": 6, "x": 6, "y": 0 },
       "datasource": { "type": "prometheus", "uid": "PBFA97CFB590B2093" },
-      "targets": [ { "expr": "sum(rate(http_requests_total{status_class=\"5xx\",job=\"farmafinder-backend\"}[5m])) / sum(rate(http_requests_total{job=\"farmafinder-backend\"}[5m]))", "legendFormat": "5xx" } ],
+      "targets": [ { "expr": "sum(rate(http_requests_total{status_class=\"5xx\",job=~\".*farmafinder-backend\"}[5m])) / sum(rate(http_requests_total{job=~\".*farmafinder-backend\"}[5m]))", "legendFormat": "5xx" } ],
       "fieldConfig": { "defaults": { "unit": "percentunit", "thresholds": { "steps": [ { "color": "green", "value": 0 }, { "color": "yellow", "value": 0.01 }, { "color": "red", "value": 0.05 } ] } } }
     },
     {
       "id": 3, "title": "CIMA errors/s", "type": "stat",
       "gridPos": { "h": 5, "w": 6, "x": 12, "y": 0 },
       "datasource": { "type": "prometheus", "uid": "PBFA97CFB590B2093" },
-      "targets": [ { "expr": "sum(rate(cima_requests_total{status=\"error\",job=\"farmafinder-backend\"}[5m]))", "legendFormat": "cima err/s" } ]
+      "targets": [ { "expr": "sum(rate(cima_requests_total{status=\"error\",job=~\".*farmafinder-backend\"}[5m]))", "legendFormat": "cima err/s" } ]
     },
     {
       "id": 4, "title": "Mobile events/s", "type": "stat",
@@ -59,6 +59,6 @@
   "timezone": "browser",
   "title": "FarmaFinder — Overview",
   "uid": "farmafinder-overview",
-  "version": 1,
+  "version": 2,
   "weekStart": ""
 }