feat(wind): add ECMWF IFS as a second wind model

Add ECMWF IFS 10 m wind alongside NOAA GFS, selectable at runtime.

The /api/wind proxy becomes a model dispatcher: `?model=gfs|ifs` (default gfs,
unknown → 400), cached per model+cycle+grid. IFS reads the keyless ECMWF Open
Data JSON Lines `.index` (note: `<stem>.index`, not `<grib2>.index`), byte-range
fetches only the `10u`/`10v` messages, decodes them with the same ecCodes WASM
path, and resamples with the existing grid code (ECMWF grids start at lo1=180;
the resampler already wraps columns).

The client layer gains a `model` parameter (setParams/getParams) with a
generation guard so a model switch aborts and refetches exactly once. Registered
as an enabled+options layer with a `model` enum.

Validated end-to-end against the real 2026-09-14 06z IFS cycle on Node 25
(180x91 grid at 2°, 131,040-byte payload, plausible mean |u|/|v|), and GFS
still passes the same check.

Attribution: contains modified Copernicus/ECMWF IFS forecast data, licensed
under CC BY 4.0. Verified: npm test (3412 pass, 0 fail), check:boundaries.

DATA_SOURCES.md

@@ -190,3 +190,5 @@ Douglas-Peucker simplification, 6-decimal rounding).
 ## In-app attribution
 
 The required Google Maps / Cesium credit renders on the on-globe credit line (`#cesium-credits`, bottom-left) and must stay visible — including in clean-view and recording modes (the whole line, logo + "Google Maps" + the "Data attribution" link, stays on screen; only the GEV panels/HUD fade). The layer-specific credits (adsb.lol, TeleGeography, OSM datacenters/dams/roads, NASA FIRMS, CelesTrak, USGS, City of Austin, Fintraffic, GBFS, Radio Browser, OpenSky, AISStream) are registered into the expandable **"Data attribution"** popover on that credit line via `viewer.creditDisplay.addStaticCredit(new Cesium.Credit(html, /* showOnScreen */ false))` — see `src/data/dataCredits.js`. When you add a new data source, add its license and attribution to this file **and** append an entry to `DATA_CREDITS` in `src/data/dataCredits.js` so it surfaces in the app.
+
+- ECMWF IFS: keyless CC BY 4.0 GRIB2 forecast data fetched via `.index` and HTTP Range. Attribution: "Contains modified Copernicus/ECMWF IFS forecast data, licensed under CC BY 4.0. Source: https://data.ecmwf.int/forecasts/".