chore: add missing i18n keys in sidebar, assets, toolbox, dropdowns (#6622)

This PR 

- adds missing locale keys for 3D viewer toast strings, assets sidebar
labels, and node error keys
- cleans up the selection toolbox, media previews, node components, and
widget uploader to rely on `$t`/`st` (exposed to template scope at
compile time) instead of importing from `useI18n`.
- updates `eslint.config.ts` to teach the Intlify rule about the locale
layout

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6622-chore-add-missing-i18n-keys-in-sidebar-assets-toolbox-dropdowns-2a36d73d365081ae8694eb4f8ebb822a)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Alexander Brown <drjkl@comfy.org>

src/renderer/extensions/vueNodes/widgets/components/WidgetFileUpload.test.ts

@@ -23,7 +23,10 @@ describe('WidgetFileUpload File Handling', () => {
       messages: {
         en: {
           ...enMessages,
-          'Drop your file or': 'Drop your file or'
+          widgetFileUpload: {
+            dropPrompt: 'Drop your file or',
+            browseFiles: 'Browse Files'
+          }
         }
       }
     })

src/renderer/extensions/vueNodes/widgets/components/WidgetFileUpload.vue

@@ -156,10 +156,12 @@
       :style="{ borderColor: '#262729' }"
     >
       <div class="flex w-full flex-col items-center gap-2 py-4">
-        <span class="text-xs opacity-60"> {{ $t('Drop your file or') }} </span>
+        <span class="text-xs opacity-60">
+          {{ $t('widgetFileUpload.dropPrompt') }}
+        </span>
         <div>
           <Button
-            label="Browse Files"
+            :label="$t('widgetFileUpload.browseFiles')"
             size="small"
             severity="secondary"
             class="text-xs"