fix(weather): queue RainViewer tiles briefly instead of failing a burst

DATA_SOURCES.md

@@ -18,7 +18,7 @@ How to read this:
 | **NOAA GFS (wind)** (`noaa-gfs-bdp-pds.s3.amazonaws.com`) | Global 10 m wind, optional 2 m temperature and mean sea-level pressure for Wind. Keyless; latest 6-hourly 0.25° cycle, byte-range GRIB2 reads, cached for an hour | U.S. public domain (NOAA); keyless via NOAA Open Data on AWS | "NOAA Global Forecast System (GFS)" (courtesy; not an endorsement) |
 | **ECMWF IFS (wind)** (`data.ecmwf.int/forecasts`, ECMWF Open Data) | The alternative Wind model: 10 m wind, optional 2 m temperature and mean sea-level pressure. Keyless; latest 6-hourly 0.25° run, byte-range GRIB2 reads, cached for an hour | [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/) plus the [ECMWF Terms of Use](https://apps.ecmwf.int/datasets/licences/general/) | "This service is based on data and products of the European Centre for Medium-Range Weather Forecasts (ECMWF)", with the CC BY 4.0 link, the modification notice and ECMWF's liability disclaimer — shown in-app |
 | **NOAA nowCOAST observed weather** (`nowcoast.noaa.gov/geoserver/observations/{weather_radar,satellite}/ows`, WMS 1.1.1) | Rain radar (MRMS base reflectivity, contiguous US, about 4-minute updates) and Satellite clouds (GOES-19/18 Band 14 regional infrared, about 5-minute updates; global infrared mosaic, hourly). Keyless; layer metadata refreshed every 2 minutes, exact-time images cached for up to 24 hours | [NOAA disclaimer](https://oceanservice.noaa.gov/disclaimer.html) | "NOAA nowCOAST · NWS/OAR MRMS radar; NESDIS GOES and global satellite partners" |
-| **RainViewer** (`api.rainviewer.com`, `tilecache.rainviewer.com`) | Rain radar, Global: past 2 hours of radar composite tiles at 10-minute steps, zoom ≤ 7. Keyless; manifest cached 5 minutes, tiles cached like other weather tiles, upstream limited to 80 tile requests a minute | [RainViewer API terms](https://www.rainviewer.com/api.html) | RainViewer (rainviewer.com), linked in-app |
+| **RainViewer** (`api.rainviewer.com`, `tilecache.rainviewer.com`) | Rain radar, Global: past 2 hours of radar composite tiles at 10-minute steps, zoom ≤ 7. Keyless; manifest cached 5 minutes, tiles cached like other weather tiles, upstream limited to 80 tile requests a minute; excess requests wait up to 20 seconds in a bounded queue | [RainViewer API terms](https://www.rainviewer.com/api.html) | RainViewer (rainviewer.com), linked in-app |
 | **NOAA nowCOAST lightning density** (`nowcoast.noaa.gov/geoserver/observations/lightning_detection/ows`) | Lightning density: 15-minute accumulated strike density on an approximately 8 km grid, Americas and Pacific. Keyless; layer metadata refreshed every 10 minutes, exact-time images cached for up to 24 hours | NOAA Level-5 derived product from Vaisala NLDN/GLD360; the [product description](https://ocean.weather.gov/lightning/lightning_pdd.php) permits public distribution of this density product, not of raw Vaisala detections | "NOAA/NWS nowCOAST; derived from Vaisala NLDN/GLD360" |
 | **NOAA NHC / CPHC advisories** (`www.nhc.noaa.gov/CurrentStorms.json` + the `mapservices.weather.noaa.gov` tropical weather summary MapServer) | Cyclone advisories: storm positions, forecast tracks, points and cones for the Atlantic and eastern/central North Pacific. Keyless through `/api/cyclones`; cached for 5 minutes | [NWS public-data terms](https://www.weather.gov/disclaimer); no endorsement implied | "NOAA/NWS NHC / CPHC" |
 | **OpenStreetMap** | Map and place data (roads, military areas and names, ALPR, place search, outlines); via vector tiles, hourly ALPR extract, bundled data, Nominatim and optional self-configured Overpass | [ODbL 1.0](https://opendatacommons.org/licenses/odbl/1-0/) | © OpenStreetMap contributors |