fix: pass temp_unit from API to WeatherCard so F/C label matches converted values

frontend/src/views/BriefingView.vue

@@ -63,11 +63,13 @@ const loadingMessages = ref(false)
 
 // Weather panel (left column)
 const weatherData = ref<WeatherData[]>([])
+const tempUnit = ref<string>('C')
 
 async function loadWeather() {
   try {
-    const data = await apiGet<{ locations: WeatherData[] }>('/api/briefing/weather')
+    const data = await apiGet<{ locations: WeatherData[]; temp_unit: string }>('/api/briefing/weather')
     weatherData.value = data.locations ?? []
+    tempUnit.value = data.temp_unit ?? 'C'
   } catch { /* silent */ }
 }
 
@@ -296,6 +298,7 @@ onMounted(async () => {
             v-for="loc in weatherData"
             :key="(loc as WeatherData).location"
             :weather="loc"
+            :temp-unit="tempUnit"
           />
         </template>
         <div v-else class="panel-empty">No weather configured</div>