feat(dashboard): console phase 3 - history, forecast accuracy, data statistics

- History in the station panel (inline SVG): 3 d / 7 d / 30 d / 90 d / 1 y /
  all or a date range; level and discharge, the 24 h peaks as the model
  issued them, warning/danger bands, hover/touch values. Up to 7 d the chart
  ends in the current forecast. Above 2,500 readings it shows the daily mean
  with the daily low-high band, so a flood peak is not averaged away; gaps
  (RID's nightly pause) break the line instead of being bridged. Days are
  Bangkok days computed arithmetically: Intl per reading took a minute for
  "All" (67,000 rows), now 2 s.
- "How accurate is the forecast?" for P.1 (/api/forecast/skill), loaded when
  opened because a cold skill query takes up to 20 s.
- Data statistics (/api/stats) behind "2.7M readings since 2018" in the
  status bar.

fix(dashboard): "All time" history ended in October 2024. The history route
returns the oldest rows first and stops at 50,000 by default; P.1 has about
67,000 hours. Both dashboards now ask for limit=100000 (the route's maximum).

docs/DASHBOARD_REDESIGN.md

@@ -1,6 +1,6 @@
 # Dashboard redesign: the console
 
-Status: **phase 2 done** (2026-10-19). The new dashboard is built next to the current
+Status: **phase 3 done** (2026-10-19). The new dashboard is built next to the current
 one and replaces it in phase 4.
 
 - **Preview:** <https://water.buildfor.life/static/console.html>, after `git pull` on the
@@ -52,8 +52,8 @@ One screen, no page scroll on a desktop:
 | Top bar | brand · **Chiang Mai verdict** (P.1 level + 24 h forecast, always visible, click selects P.1) · gauges reporting · highest 24 h flood chance · data age · EN/ไทย · light/dark · Get alerts |
 | Left | two lists: **RID gauges** (status bar, code, name, margin to the warning level, 72 h sparkline, level and 6 h change; sort by river order, closest to the warning level, rising) and **Basin stations** (ThaiWater/HII: % of bank height, river and agency; sort fullest first or by name); filter; legend |
 | Centre | map on a self-hosted vector basemap (labels in the page language): Ping mainstem and tributaries, gauges coloured by status with code + level labels, layers Basin stations (diamonds), Rain 24 h and Flood zones, the team's markers from zoom 12, one legend |
-| Right | selected RID gauge: level, 6 h change, discharge, warning/danger level with margins, capacity; level scale with now and 24 h peak; 72 h chart with the forecast peaks; forecast table (peak, chance of warning/danger at 6/12/24 h, model, issue time, disclaimer); for P.1 the seven inundation stages and the zones toggle; data links. A basin station shows level (m MSL), % of bank height with ThaiWater's class, distance to and height of the bank top, gauge reading, agency (latest reading only: no history is kept for them) |
-| Status bar | data credits, API, source code |
+| Right | selected RID gauge: level, 6 h change, discharge, warning/danger level with margins, capacity; level scale with now and 24 h peak; history (3 d / 7 d / 30 d / 90 d / 1 y / all or dates: level, discharge, the 24 h peaks as issued, warning/danger bands, hover values; up to 7 d it ends in the current forecast); forecast table (peak, chance of warning/danger at 6/12/24 h, model, issue time, disclaimer); for P.1 the seven inundation stages, the zones toggle and "How accurate is the forecast?"; data links. A basin station shows level (m MSL), % of bank height with ThaiWater's class, distance to and height of the bank top, gauge reading, agency (latest reading only: no history is kept for them) |
+| Status bar | data credits, "2.7M readings since 2018" (opens the data statistics), API, source code |
 
 **Narrower screens:**
 
@@ -110,6 +110,8 @@ One screen, no page scroll on a desktop:
 - **Rain layer:** off by default unless any station has heavy rain (> 35 mm / 24 h); an explicit choice is remembered.
 - **Flood zones:** shown automatically while P.1 is at or above a stage, unless hidden by the user.
 - **Basin stations:** ThaiWater's classes for the level as a share of the bank height (critically low ≤ 10 %, low ≤ 30 %, normal ≤ 70 %, high ≤ 100 %, over the bank). On the map and in the list over the bank is danger, high is watch, the rest normal; no data after 24 h. Gauges RID already lists are shown once, as RID gauges. The layer is off until the list is opened or the button pressed.
+- **History:** above 2,500 readings (30 d and longer for most gauges) the chart shows the daily mean with the daily low–high band, so a flood peak is not averaged away; gaps longer than 3.5 h (2.5 days when daily) break the line rather than bridging RID's nightly pause. Short ranges reload with every refresh, long ones at most hourly. "All" asks for `limit=100000`: `/measurements/history` returns the oldest rows first and stops at its 50,000 default, which made the current dashboard's "All time" for P.1 end in October 2024 (fixed there too).
+- **Forecast accuracy:** loaded when the section is opened (a cold `/api/forecast/skill` query takes up to 20 s), cached for 15 minutes; bias and persistence error are in each row's tooltip.
 - **Basemap:** `src/static/basemap/ping-basin.pmtiles`, a Protomaps extract (bbox 97.85–99.95 E, 16.85–20.2 N, zoom 0–12, 15 MB, OpenStreetMap data), drawn by protomaps-leaflet 5.1.0 in its `light`/`dark` style with `name:th`/`name:en` labels. Refresh instructions in `src/static/basemap/README.md`. The map cannot be panned far outside the basin. OSM raster tiles are the fallback if the renderer does not load.
 
 ## Phases
@@ -128,9 +130,9 @@ Each phase is one commit, checked with screenshots: 1440, 1100 and 390 px; light
    - **Server:** ServeDir answers HTTP range requests (checked: 206); `dev_proxy.py` now does too.
    - **ThaiWater/HII stations:** the Basin stations list and map layer, from `/api/hii/waterlevel/latest`, falling back to `/sensors/thaiwater`.
    - **Custom markers:** `custom-markers.json` as pins, with their flood-zone popup.
-3. **Station depth.**
-   - **History in the panel:** range 24 h / 7 d / 30 d / 90 d / all / custom dates, level and discharge, issued 24 h forecasts overlaid, flood bands; Chart.js or SVG.
-   - **P.1 forecast skill** ("Is the model getting better?") as a panel section, from `/api/forecast/skill`.
+3. **Done — Station depth.**
+   - **History in the panel** (inline SVG, no chart library): ranges and dates, level and discharge, issued 24 h forecasts overlaid, warning/danger bands, hover/touch values.
+   - **P.1 forecast accuracy** as a collapsible panel section, from `/api/forecast/skill`.
    - **Data statistics:** a status-bar popover, from `/api/stats`.
 4. **Modes and the swap.**
    - **October 2024 replay:** banner, clock, markers and verdict follow the replay; zones auto-show.