Merge ticket/023-dashboards-refresh-with-ui

Resolves a POLL_MS import conflict with ticket 025 in App.tsx.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XFUNZwCvz3kcod3352ZR2o

webapp/src/lib/polling.ts

@@ -0,0 +1,4 @@
+/// Shared polling cadence for the whole app — the log/timeline poll in `App.tsx` and any
+/// other section that should refresh on the same rhythm (e.g. dashboard panels) import this
+/// instead of hardcoding their own interval, so they can never drift apart.
+export const POLL_MS = 2000