New standalone WeatherSource entity with pluggable provider architecture
(Open-Meteo v1, free, no API key). Full CRUD, test endpoint, browser
geolocation, IconSelect provider picker, CardSection with test/clone/edit.
WeatherColorStripStream maps WMO weather codes to ambient color palettes
with temperature hue shifting and thunderstorm flash effects. Ref-counted
WeatherManager polls API and caches data per source.
CSS editor integration: weather type with EntitySelect source picker,
speed and temperature influence sliders. Backup/restore support.
i18n for en/ru/zh.
