feat(dashboard): console phase 4 - 2024 replay, simulation, replaces the old page

The console is now the dashboard at / (src/static/dashboard.html); the old
page and console.html are gone.

- Replay of the October 2024 flood (flood-2024-all.json): the page's clock,
  verdict, list, markers, flood zones and panel follow the replay; the panel
  charts the season on fixed axes with the 2024 model's 24 h peak. Hourly
  while the model alerts or P.1 is above 3.50 m, faster through quiet days;
  pause and drag. Rain, basin stations and the 5-minute refresh are off
  during the replay (today's data).
- ?demo_level= and ?demo_rise= simulate P.1. A violet REPLAY / amber
  SIMULATION bar, the top bar's KPI and the P.1 panel say so; the mode is
  drawn from state.mode alone, so a refresh or language switch cannot
  relabel either as live.
- History: rows without discharge_percent are ThaiWater's copy of the gauge
  (night hours RID publishes late), with a different rating (P.1: 26 against
  RID's 54 m3/s); their discharge is not drawn for gauges with RID discharge.
  The discharge strip has headroom so its label stays clear of the line.
- Swap: the old page's title, description, Open Graph and JSON-LD tags; no
  noindex; tests/test_dashboard.py = console tests + the old checks that
  still apply (one P.1 level, SEO files) + a replay/simulation labelling test.
- Docs: README screenshot (docs/img/dashboard.jpg, replacing two unused
  images), CLAUDE.md, CONTRIBUTING.md, FLOOD_FORECASTING.md (where the model
  shows), DASHBOARD_REDESIGN.md (phase 4 done, mode rules).

Deploy needs a restart: the server reads dashboard.html at start.

README.md

@@ -11,6 +11,8 @@ a gauge crosses its warning or danger level.
 after the [October 2024 flood](https://buildfor.life/blog/chiang-mai-flood-2024/) —
 background in [Teaching a Model to See the Ping River Rise 13 Hours Early](https://buildfor.life/blog/ping-river-monitor/).
 
+![The dashboard: Chiang Mai's flood verdict and the gauges in the top bar, the gauge list, the map and the panel for P.1 Nawarat Bridge with its history and forecast](docs/img/dashboard.jpg)
+
 [![CI](https://git.b4l.co.th/B4L/Northern-Thailand-Ping-River-Monitor/actions/workflows/ci.yml/badge.svg)](https://git.b4l.co.th/B4L/Northern-Thailand-Ping-River-Monitor/actions)
 [![Rust](https://git.b4l.co.th/B4L/Northern-Thailand-Ping-River-Monitor/actions/workflows/rust.yml/badge.svg)](https://git.b4l.co.th/B4L/Northern-Thailand-Ping-River-Monitor/actions)
 [![Security](https://git.b4l.co.th/B4L/Northern-Thailand-Ping-River-Monitor/actions/workflows/security.yml/badge.svg)](https://git.b4l.co.th/B4L/Northern-Thailand-Ping-River-Monitor/actions)
@@ -35,9 +37,11 @@ background in [Teaching a Model to See the Ping River Rise 13 Hours Early](https
   data through August 2024, the first alert came **13 hours before** P.1 crossed
   3.70 m. Everything about the model, including what did not work:
   [docs/FLOOD_FORECASTING.md](docs/FLOOD_FORECASTING.md).
-- **Shows it.** A Leaflet map with the river drawn as OSM geometry and styled by live
-  discharge, rain gauges, the Chiang Mai inundation zones, per-station history, the
-  forecast card, a replay of the 2024 flood, English/Thai, light/dark.
+- **Shows it.** One screen: Chiang Mai's flood verdict, the gauges with their status
+  and trend, a self-hosted map of the basin with rain and the city's inundation
+  zones, and a panel per station with its history since 2018, the forecast and how
+  accurate it has been. ThaiWater's basin stations, a replay of the 2024 flood,
+  Thai/English, dark/light.
 - **Notifies.** Public push alerts over a self-hosted [ntfy](https://ntfy.sh): one
   message when a gauge crosses its warning or danger level, one all-clear on the
   way down, an opt-in early-warning topic from the model, nothing in between.
@@ -176,7 +180,7 @@ 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/DASHBOARD_REDESIGN.md](docs/DASHBOARD_REDESIGN.md) — the dashboard: layout, rules, how it replaced the old page
 - [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/)