feat(p1): city flood stages and zones from CMU Water Center's 2024 flood map

CMU Water Center's Chiang Mai flood hazard map (CMFlood) replaces the older
municipal map. It is built on the October 2024 flood and has the Ping leave
its banks above P.1 4.20 m, with five stages: 4.30, 4.50, 4.70, 5.00 and
5.30 m (the 2024 record). The old map's seven stages (3.70-4.60 m) said the
city floods from 3.70 m; CMU calls that map out of date.

- P1_FLOOD_STAGES: the five CMU stages, discharge on RID's 2024 rating.
  /forecast's P.1 `stages` now has five entries (same format). Thresholds
  are unchanged: 4.20 m danger is the bank top, 3.70 m warning half a metre
  below (as on CMU's gauge page). flood_config.json and the Rust parity
  fixtures regenerated (only the stages changed).
- flood-zones-p1.geojson: CMU's KML (L1..L5) as five disjoint zones, zone k
  floods first at stage k; scripts/build_flood_zones.py rebuilds it.
- Dashboard: CMU's colours and credit (map attribution); the stage grid follows
  the number of stages; zone lookup for markers honours holes. The city
  verdict uses statusOf's classes: flooding (over the banks) from 4.20 m,
  high water from 3.70 m. Zones show by themselves when the river is over its
  banks or stage 1 is >= 50 % likely. Alert, replay and verdict texts no
  longer call 3.70 m city flooding (EN + TH).
- Docs: DATA_SOURCES 5.1 (CMFlood: the map, flood marks, poles, city gauges),
  FLOOD_FORECASTING, DASHBOARD_REDESIGN, NOTIFICATIONS, README credits.

docs/DATA_SOURCES.md

@@ -235,6 +235,34 @@ Oct 2024 flood). Mae Kuang Udom Thara is the second upstream reservoir.
 | `https://hydro-1.net` | RID Upper-Northern Hydrology Center — hourly/daily tables, hydrology yearbooks (rating curves) for P-series stations; scrape/download |
 | `https://water.rid.go.th/flood/flood/daily.pdf` | RID daily flood bulletin (PDF only) |
 
+### 5.1 CMU Water Center — CMFlood (Chiang Mai city) (verified 2026-10-25)
+
+`https://watercenter.cmu.ac.th/chiangmai/cmflood/warning/*`, the Chiang Mai urban
+flood warning site of Chiang Mai University's water center (with RID, ONWR, DDPM
+and the province). A Next.js app; its data paths are in the page chunks
+(`/_next/static/chunks/app/...`). No licence is stated; we credit CMU.
+
+- **Flood hazard map, 2024 flood** — `/data/KML5Layer/L1.kml` … `L5.kml`: the
+  flooded extent at P.1 = 4.30 / 4.50 / 4.70 / 5.00 / 5.30 m (2.5 / 3.0 / 22 / 57 /
+  156 km², cumulative). CMU: the Ping overflows its banks above P.1 4.20 m, and the
+  older municipal map (2011 flood) no longer fits the city's defences. **In use:**
+  `P1_FLOOD_STAGES` and `src/static/flood-zones-p1.geojson`
+  (`uv run scripts/build_flood_zones.py`).
+- **Flood marks 2024** — `/data/New_floodMark_2025_fixed_like_pole.geojson` (4.9 MB):
+  4,869 points in Chiang Mai and Lamphun with the October 2024 depth above the road
+  in cm (P.1 = 5.30 m), the marker's place and type.
+- **Flood poles** — `/data/PoleCNX2025_v2.geojson`: 219 poles with ground level and
+  maximum flood level (m MSL) and the depth.
+- **City-reach gauges** (station page): P.67, P.103, P.1, P.104 (RID, `ST.16`
+  every 15 min), FloodBoy FBP.2/FBP.3 (CMU climate data centre) and DDPM CMI01–03
+  (camera gauges, ~5 min, public CCTV snapshots), with gauge zero, bank levels
+  and chainage. CMU reads them from its own Supabase project with a public browser
+  key (tables `disaster_level`, `flagship_hydro`, `water_levels`, `hydro_levels`;
+  timestamps are Bangkok time labelled `+00:00`); history starts 2026-08 (FBP
+  2025-09). Not ingested: too short to train on, and polling CMU's database is
+  using their infrastructure — prefer the original sources or ask CMU.
+- **P.1 forecast** (`floodforecast`): login only.
+
 ---
 
 ## 6. Integration status & recommended order
@@ -250,6 +278,8 @@ Oct 2024 flood). Mae Kuang Udom Thara is the second upstream reservoir.
 | Satellite QPE (GSMaP/IMERG) | ❌ | Backfill training rainfall (GEE) |
 | Open-Meteo rain | ✅ Hourly by ping-collector → `openmeteo_rain` (5 catchment points, past 5 days + 48 h forecast); the 2021+ archive trains the hgb-v3 rain features | — |
 | HII API key (dams, forecasts) | ❌ | Contact HII for sanctioned access |
+| CMU CMFlood flood map (2024) | ✅ Static (2026-10-25): P.1 stages and the city's flood zones | Rebuild with `scripts/build_flood_zones.py` if CMU revises the map |
+| CMU CMFlood marks, poles, city gauges | ❌ | See 5.1 |
 
 **Collector configuration** (ping-collector): HII, the dams and Open-Meteo are
 fetched once per clock hour, also while RID is being retried; one-shot via