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Adds internal/prom package with histograms for HTTP, GORM, B2, APNs, and FCM, wired into the Echo router (HTTPMiddleware + /metrics) and GORM via statement-level callbacks (no ctx plumbing needed). Storage and push clients call ObserveB2Upload / ObserveAPNsSend / ObserveFCMSend at the network round-trip points. Existing internal/monitoring metrics move to /metrics/legacy so the canonical /metrics emits proper histogram buckets for p50/p95/p99 rollups. deploy-k3s/manifests/observability/vmagent.yaml deploys a single-replica vmagent in the honeydue namespace that scrapes api Pods on :8000/metrics every 15s and remote-writes to https://obs.88oakapps.com/api/v1/write with a bearer token (substituted at deploy time from OBS_INGEST_TOKEN in deploy/prod.env). NetworkPolicies allow vmagent egress to api Pods and to the public obs endpoint over :443; the obs side runs VictoriaMetrics + Jaeger + Grafana on 88oakappsUpdate. docs/observability-plan.md captures the full plan including resource budget, instrumentation table, 4-step rollout, and migration triggers. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>