Even further app fixes (#9617)

- Allow dragging zoom pane with middle click
- Prevent selection of canvasOnly widgets
- These widgets would not display in app mode, so allow selection would
only cause confusion.
- Support displaying the error dialogue in app mode
- Add a somewhat involved mobile app mode error indication system
<img width="300" alt="image"
src="https://github.com/user-attachments/assets/d8793bbd-fff5-4b2a-a316-6ff154bae2c4"
/> <img width="300" alt="image"
src="https://github.com/user-attachments/assets/cb88b0f6-f7e5-409e-ae43-f1348f946b19"
/>

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9617-Even-further-app-fixes-31d6d73d365081c891dfdfe3477cfd61)
by [Unito](https://www.unito.io)

src/views/LinearView.vue

@@ -9,6 +9,7 @@ import { computed, useTemplateRef } from 'vue'
 import AppBuilder from '@/components/builder/AppBuilder.vue'
 import AppModeToolbar from '@/components/appMode/AppModeToolbar.vue'
 import ExtensionSlot from '@/components/common/ExtensionSlot.vue'
+import ErrorOverlay from '@/components/error/ErrorOverlay.vue'
 import TopbarBadges from '@/components/topbar/TopbarBadges.vue'
 import TopbarSubscribeButton from '@/components/topbar/TopbarSubscribeButton.vue'
 import WorkflowTabs from '@/components/topbar/WorkflowTabs.vue'
@@ -156,6 +157,7 @@ const linearWorkflowRef = useTemplateRef('linearWorkflowRef')
         </div>
         <div ref="bottomLeftRef" class="absolute bottom-7 left-4 z-20" />
         <div ref="bottomRightRef" class="absolute right-4 bottom-7 z-20" />
+        <div class="absolute top-4 right-4 z-20"><ErrorOverlay app-mode /></div>
       </SplitterPanel>
       <SplitterPanel
         v-if="hasRightPanel"