fix: refresh public dashboard and BI telemetry

.project-docs/50-evidence/topics/2026-08-03-channel-bi-freshness.md

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+# Channel BI freshness after August publication
+
+## Question
+
+The operator reported that the monthly report had updated but Channel BI still showed `8.1`.
+
+## Read-only evidence
+
+- `reporting.monthly_runs` has active August V02 with `as_of_date=2026-08-02`, 268 rows and 6 channels. August V01
+  at `2026-08-01` is superseded.
+- A fresh `PostgresAnalyticsRepository.read_dashboard("2026-08")` repeatable-read query returns
+  `max_arrival_date=2026-08-02`, `min_arrival_date=2026-08-01`, `updated_at=2026-08-03T14:21:29+08:00` and 268
+  retained rows. The source projection and database publication are therefore current.
+- `arr_web/static/app.js` calls `loadAnalytics()` during initial boot, on the first BI tab entry only when
+  `state.analytics` is empty, and when the month selector changes. The existing four-second timer belongs to the
+  monthly-history list and does not refresh BI analytics.
+
+## Conclusion
+
+This is a frontend freshness bug, not an operator mistake and not a current monthly-worker/database publication
+failure. A BI page opened before V02 was published can keep rendering the cached 8.1 payload until the page reloads or
+the month selector changes. No code, runtime, report or business data was changed during diagnosis.
+
+## Repair implemented
+
+`arr_web/static/app.js` and `arr_web/static/h5.js` now check the selected month's lightweight `updated_at` metadata
+every five seconds while visible. They reload the full analytics payload only when the selected month changes or its
+`updated_at` changes, pause while hidden, check immediately when visible again and preserve the last good snapshot on
+transient background failures. The desktop monthly-history timer remains four seconds and is independent from BI.
+
+Focused verification passes: BI visual/static contract 5/5, Web contract 19/19, both JavaScript syntax checks and
+`git diff --check`. No API, report or business data behavior changed.