From 12a97a59faa00e55170d4403dc0466ff5dbfa840 Mon Sep 17 00:00:00 2001
From: rock <locartrock@gmail.com>
Date: Sun, 13 Sep 2026 21:49:03 +0900
Subject: [PATCH] feat(O9): Postgres internal observability

- DB pool size/idle/active gauges updated every 60s (background task)
- DB query total/errors counters defined
- DB query/transaction duration histograms defined
- Table row count gauges (entity, edge, chunk) updated periodically
- Deep PG stats (pg_stat_*, pg_statio_*) collected by pg_exporter
- Metrics: PG1-PG33 (app-visible subset, rest from pg_exporter)