fix(weather): robust location resolution with parallel fetch and multi-tier fallback (#2638)

Decouple weather data fetching from reverse geocoding so that
weather loads as soon as coordinates are available, even when
Nominatim is unreachable (e.g. mainland China).

- Fetch Open-Meteo weather immediately once lat/lon are known.
- Resolve city name in parallel via Nominatim -> Photon -> BigDataCloud.
- If all reverse geocoding fails, keep displaying weather with a
  placeholder city name.
- Skip reverse geocoding entirely when the user has configured a
  city name.
- Fall back to ip-api.com when GeoClue2 is unavailable or returns
  zero coordinates.
- Add request-generation tracking to discard stale geocoding
  responses after location changes.
- Hold explicit WeatherService refs in bar widget and dashboard tab.

Co-authored-by: lingdiansr <2077258365@qq.com>

quickshell/Modules/DankDash/WeatherTab.qml

@@ -18,6 +18,9 @@ Item {
     property bool showHourly: false
     property bool available: WeatherService.weather.available
 
+    Component.onCompleted: WeatherService.addRef()
+    Component.onDestruction: WeatherService.removeRef()
+
     function syncFrom(type) {
         if (!dailyLoader.item || !hourlyLoader.item)
             return;