feat(nav): teleport Gallery Select into the nav action slot

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/views/GalleryView.vue

@@ -1,13 +1,13 @@
 <template>
   <v-container fluid class="py-6">
-    <div class="fc-gallery-toolbar">
+    <Teleport to="#fc-nav-actions">
       <v-btn
         :color="sel.isSelectMode ? 'accent' : undefined"
         :variant="sel.isSelectMode ? 'flat' : 'tonal'"
         size="small"
         @click="sel.isSelectMode ? sel.exitSelectMode() : sel.enterSelectMode()"
       >{{ sel.isSelectMode ? 'Done' : 'Select' }}</v-btn>
-    </div>
+    </Teleport>
 
     <div class="fc-gallery-layout">
       <div class="fc-gallery-layout__main">
@@ -83,9 +83,6 @@ function closeImage() {
 }
 .fc-gallery-layout__main { flex: 1; min-width: 0; }
 .fc-gallery-layout__sidebar { flex-shrink: 0; }
-.fc-gallery-toolbar {
-  display: flex; justify-content: flex-end; margin-bottom: 12px;
-}
 
 @media (max-width: 900px) {
   .fc-gallery-layout { flex-direction: column-reverse; }