feat(ui): hidden-view review strip — flagged auto-hides with keep / un-hide (#141 step 5)

When "Show hidden" is on, a review strip appears atop the gallery listing the
auto-hidden chrome flagged "also looks like content" (most-concerning first):
thumbnail + "also looks like <X>" + Keep hidden / Un-hide. Un-hide removes the
presentation tag (image returns to the gallery) and trains the head; Keep
resolves the flag. Self-hides when there's nothing to review; theme-token styled.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CDgx8bQS5YrGRK76v8HUnM

frontend/src/views/GalleryView.vue

@@ -13,6 +13,7 @@
       <div class="fc-gallery-layout__main">
         <PostInfoHeader />
         <GalleryFilterBar v-if="store.filter.post_id == null" />
+        <HiddenReviewStrip />
         <EmptyState v-if="store.isEmpty" />
         <GalleryGrid v-else @open="openImage" />
       </div>
@@ -33,6 +34,7 @@ import { useGalleryStore } from '../stores/gallery.js'
 import { useModalStore } from '../stores/modal.js'
 import GalleryGrid from '../components/gallery/GalleryGrid.vue'
 import GalleryFilterBar from '../components/gallery/GalleryFilterBar.vue'
+import HiddenReviewStrip from '../components/gallery/HiddenReviewStrip.vue'
 import TimelineSidebar from '../components/gallery/TimelineSidebar.vue'
 import EmptyState from '../components/gallery/EmptyState.vue'
 import PostInfoHeader from '../components/gallery/PostInfoHeader.vue'