FIX - keep CityWarn rendering crisp

Disable the persistent compositor hint for the CityWarn app window so text does not alternate between blurred and sharp states during interaction. Keep the exception scoped to CityWarn and cover the host-class contract.

frontend/src/views/PhoneAppWindow.contract.test.ts

@@ -15,5 +15,6 @@ describe('PhoneAppWindow bundle contract', () => {
     expect(source).toContain("app.value?.id === 'app-store'")
     expect(source).toContain('? AppStoreApp : app.value?.component')
     expect(source).toContain('<component :is="builtinAppComponent" />')
+    expect(source).toContain("'app-window--citywarn': app.id === 'citywarn'")
   })
 })

frontend/src/views/PhoneAppWindow.vue

@@ -27,7 +27,12 @@ const launchStyle = computed(() => {
 </script>
 
 <template>
-  <div v-if="app" class="app-window" :style="launchStyle">
+  <div
+    v-if="app"
+    class="app-window"
+    :class="{ 'app-window--citywarn': app.id === 'citywarn' }"
+    :style="launchStyle"
+  >
     <CustomAppFrame
       v-if="isExternalPhoneApp(app)"
       :key="getCustomAppFrameKey(app)"