feat(dashboard): the console, phase 1 of the redesign (preview at /static/console.html)

The user chose direction B of the redesign: a full-screen operations console.
It is built next to the current dashboard, served by ServeDir at
/static/console.html (noindex, links back to /), and replaces dashboard.html
once it covers every feature (docs/DASHBOARD_REDESIGN.md, phase 4).

Phase 1:
- top bar: the Chiang Mai verdict (P.1 level + 24 h forecast, the current
  dashboard's rule), gauges reporting, highest 24 h flood chance, data age
  ("overnight pause" instead of "stale" during RID's nightly gap, as in the
  notifier), EN/TH, light/dark (dark default), Get alerts
- gauge list: one status rule for list, map and panel (normal, watch within
  0.5 m or >= 25 % chance, warning, danger, no data), margin to the warning
  level, 72 h sparkline, 6 h change; filter; sort by river order, closest to
  the warning level, rising; arrow keys
- map: Ping mainstem and tributaries, status markers with code + level,
  layers Rain 24 h (on by default only with heavy rain) and Flood zones
  (auto-shown while P.1 is at a stage), one legend
- station panel: level, change, discharge (last RID value when the newest
  hour is level-only), warning/danger levels with margins, capacity, level
  scale with now and 24 h peak, 72 h chart with the forecast peaks, forecast
  table with the model and issue time, the P.1 inundation stages, data links
- alerts drawer with the ntfy topics; selection in the URL (#P.84); refresh
  every 5 minutes
- Inter and Noto Sans Thai self-hosted (src/static/fonts, 75 KB, OFL), no
  emoji, Thai first, Bangkok time

tests/test_console.py: routed fetch paths, EN/TH parity, translated aria
labels, no emoji, fonts and licences, noindex. dev_proxy.py serves
src/static with real content types (it sent HTML as octet-stream).

README.md

@@ -176,6 +176,7 @@ models/              trained bundles (gitignored) and evaluation results
 - [docs/MATRIX_QUICK_START.md](docs/MATRIX_QUICK_START.md) — the same alerts in a Matrix room
 - [rust/README.md](rust/README.md) — the service: commands, configuration, develop, deploy
 - [docs/RUST_REWRITE.md](docs/RUST_REWRITE.md) — why and how it moved from Python to Rust
+- [docs/DASHBOARD_REDESIGN.md](docs/DASHBOARD_REDESIGN.md) — the new console dashboard (preview at `/static/console.html`): layout, rules, phases
 - [docs/references/NOTABLE_DOCUMENTS.md](docs/references/NOTABLE_DOCUMENTS.md) — official Thai government resources
 - Public overview: [buildfor.life/docs/tooling/ping-river-monitor](https://buildfor.life/docs/tooling/ping-river-monitor/)