feat(10-09): plumb keyboard shortcut ref chain — DropZone→SearchBar→StorageBrowser→FileManagerView

- DropZone: defineExpose({ triggerInput }) to expose file picker trigger
- SearchBar: add inputEl ref + defineExpose({ focus }) for / shortcut
- StorageBrowser: add dropZoneRef + searchBarRef; expand defineExpose to include triggerUpload, focusSearch, clearSearch
- FileManagerView: add defineExpose delegating all four methods to browserRef via optional chaining

frontend/src/components/storage/StorageBrowser.vue

@@ -10,7 +10,7 @@
           @navigate="$emit('breadcrumb-navigate', $event)"
         />
         <div class="ml-auto flex items-center gap-2 shrink-0">
-          <SearchBar v-if="showSearch" :model-value="searchQuery" @update:modelValue="$emit('search-change', $event)" />
+          <SearchBar v-if="showSearch" ref="searchBarRef" :model-value="searchQuery" @update:modelValue="$emit('search-change', $event)" />
           <SortControls
             v-if="showSearch"
             :sort="sortField"
@@ -36,7 +36,7 @@
 
       <!-- Upload zone -->
       <div class="px-6 pt-5 pb-3">
-        <DropZone @files-selected="$emit('upload', $event)" />
+        <DropZone ref="dropZoneRef" @files-selected="$emit('upload', $event)" />
         <UploadProgress :items="uploadQueue" />
       </div>
 
@@ -321,6 +321,11 @@ function topicColor(name) {
   return props.topicColorFn(name)
 }
 
+// ── Child component refs ──────────────────────────────────────────────────────
+
+const dropZoneRef = ref(null)
+const searchBarRef = ref(null)
+
 // ── New folder inline input ───────────────────────────────────────────────────
 
 const showNewFolderInput = ref(false)
@@ -346,8 +351,12 @@ async function submitNewFolder() {
   emit('folder-create', { name, onError: (msg) => { newFolderError.value = msg }, onSuccess: cancelNewFolder })
 }
 
-/** Called by the parent view when the toolbar "New folder" button is clicked. */
-defineExpose({ startNewFolder })
+defineExpose({
+  startNewFolder,
+  triggerUpload: () => dropZoneRef.value?.triggerInput(),
+  focusSearch: () => searchBarRef.value?.focus(),
+  clearSearch: () => emit('search-change', ''),
+})
 
 // ── Rename ────────────────────────────────────────────────────────────────────