Fix stale weather temp — fetch independently of weather card

[asim]

The weather summary next to the date was reading from localStorage but only the weather card ever wrote to it. Since we removed the card, the cached value was frozen at whatever it was last time the card rendered.

Now the date-line weather script runs its own fetch cycle:

1. Show cached value immediately (no flash of empty)
2. If cache is older than 1 hour, fetch fresh data from /weather
3. Uses the same lat/lon localStorage keys the card used
4. If no cached location, requests geolocation (same as card did)
5. Updates localStorage and the displayed temp on success

Works whether or not the weather card is visible. The card and the date-line share the lat/lon keys but the summary has its own cache key (mu_weather_now + mu_weather_now_ts) so they don't conflict.