Add image listing and asset management

Show images in asset directories with preview, rename, replacement, and trash recovery. Update local Markdown references when images move and restore original files if related metadata cannot be committed.

Refresh image previews after replacement and compare actual contents when deduplicating subsequent uploads.

web/src/app/Workspace.vue

@@ -7,6 +7,7 @@ import Icon from './Icon.vue'
 import MobileToolbar from './MobileToolbar.vue'
 import MoveDialog from './MoveDialog.vue'
 import ImportDialog from './ImportDialog.vue'
+import ImageDialog from './ImageDialog.vue'
 import NoteBanner from './NoteBanner.vue'
 import OutlinePanel from './OutlinePanel.vue'
 import QuickSwitcher from './QuickSwitcher.vue'
@@ -122,6 +123,7 @@ onBeforeUnmount(() => {
     <SettingsDialog v-if="ws.settings" />
     <ShareDialog v-if="ws.sharing" :path="ws.sharing" @close="ws.sharing = null" />
     <ImportDialog v-if="ws.importing !== null" :dir="ws.importing" @close="ws.importing = null" />
+    <ImageDialog v-if="ws.image" :path="ws.image" />
     <MoveDialog v-if="ws.moving" :path="ws.moving" @close="ws.moving = null" />
   </div>
 </template>