Decouple Desktop UI into monorepo app (#5912)

## Summary

Extracts desktop UI into apps/desktop-ui package with minimal changes.

## Changes

- **What**:
- Separates desktop-specific code into standalone package with
independent Vite config, router, and i18n
- Drastically simplifies the main app router by removing all desktop
routes
  - Adds a some code duplication, most due to the existing design
- Some duplication can be refactored to be *simpler* on either side - no
need to split things by `isElectron()`
  - Rudimentary storybook support has been added
- **Breaking**: Stacked PR for publishing must be merged before this PR
makes it to stable core (but publishing _could_ be done manually)
  - #5915
- **Dependencies**: Takes full advantage of pnpm catalog. No additional
dependencies added.

## Review Focus

- Should be no changes to normal frontend operation
- Scripts added to root package.json are acceptable
- The duplication in this PR is copied as is, wherever possible. Any
corrections or fix-ups beyond the scope of simply migrating the
functionality as-is, can be addressed in later PRs. That said, if any
changes are made, it instantly becomes more difficult to separate the
duplicated code out into a shared utility.
  - Tracking issue to address concerns: #5925

### i18n

Fixing i18n is out of scope for this PR. It is a larger task that we
should consider carefully and implement properly. Attempting to isolate
the desktop i18n and duplicate the _current_ localisation scripts would
be wasted energy.

apps/desktop-ui/src/components/common/RefreshButton.vue

@@ -0,0 +1,52 @@
+<!--
+  A refresh button that disables and shows a progress spinner whilst active.
+
+  Usage:
+  ```vue
+    <RefreshButton
+      v-model="isRefreshing"
+      :outlined="false"
+      @refresh="refresh"
+    />
+  ```
+-->
+<template>
+  <Button
+    class="relative p-button-icon-only"
+    :outlined="outlined"
+    :severity="severity"
+    :disabled="active || disabled"
+    @click="(event) => $emit('refresh', event)"
+  >
+    <span
+      class="p-button-icon pi pi-refresh transition-all"
+      :class="{ 'opacity-0': active }"
+      data-pc-section="icon"
+    />
+    <span class="p-button-label" data-pc-section="label">&nbsp;</span>
+    <ProgressSpinner v-show="active" class="absolute w-1/2 h-1/2" />
+  </Button>
+</template>
+
+<script setup lang="ts">
+import Button from 'primevue/button'
+import ProgressSpinner from 'primevue/progressspinner'
+
+import type { PrimeVueSeverity } from '@/types/primeVueTypes'
+
+const {
+  disabled,
+  outlined = true,
+  severity = 'secondary'
+} = defineProps<{
+  disabled?: boolean
+  outlined?: boolean
+  severity?: PrimeVueSeverity
+}>()
+
+// Model
+const active = defineModel<boolean>({ required: true })
+
+// Emits
+defineEmits(['refresh'])
+</script>