feat(web): warn before overwriting existing locations in geolocation utility (#28840)

i18n/en.json

@@ -2248,6 +2248,7 @@
   "slideshow_repeat_description": "Loop back to beginning when slideshow ends",
   "slideshow_settings": "Slideshow settings",
   "smart_album": "Smart album",
+  "some_assets_already_have_a_location_warning": "Some of the selected assets already have a location",
   "sort_albums_by": "Sort albums by...",
   "sort_created": "Date created",
   "sort_items": "Number of items",

web/src/lib/modals/GeolocationUpdateConfirmModal.svelte

@@ -1,6 +1,7 @@
 <script lang="ts">
+  import { assetMultiSelectManager } from '$lib/managers/asset-multi-select-manager.svelte';
   import type { LatLng } from '$lib/types';
-  import { ConfirmModal } from '@immich/ui';
+  import { Alert, ConfirmModal } from '@immich/ui';
   import { t } from 'svelte-i18n';
 
   type Props = {
@@ -9,11 +10,18 @@
     onClose: (confirm: boolean) => void;
   };
 
-  let { point, assetCount, onClose }: Props = $props();
+  const { point, assetCount, onClose }: Props = $props();
+
+  const hasExistingLocations = $derived(
+    assetMultiSelectManager.assets.some((asset) => asset.latitude != null || asset.longitude != null),
+  );
 </script>
 
 <ConfirmModal title={$t('confirm')} size="small" confirmColor="primary" {onClose}>
   {#snippet prompt()}
+    {#if hasExistingLocations}
+      <Alert color="warning" class="mb-4">{$t('some_assets_already_have_a_location_warning')}</Alert>
+    {/if}
     <p>{$t('update_location_action_prompt', { values: { count: assetCount } })}</p>
     <p>- {$t('latitude')}: {point.lat}</p>
     <p>- {$t('longitude')}: {point.lng}</p>