feat: add weather source entity and weather-reactive CSS source type

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.

server/src/wled_controller/api/__init__.py

@@ -24,6 +24,7 @@ from .routes.webhooks import router as webhooks_router
 from .routes.sync_clocks import router as sync_clocks_router
 from .routes.color_strip_processing import router as cspt_router
 from .routes.gradients import router as gradients_router
+from .routes.weather_sources import router as weather_sources_router
 
 router = APIRouter()
 router.include_router(system_router)
@@ -48,5 +49,6 @@ router.include_router(webhooks_router)
 router.include_router(sync_clocks_router)
 router.include_router(cspt_router)
 router.include_router(gradients_router)
+router.include_router(weather_sources_router)
 
 __all__ = ["router"]