fix(ui): mobile responsiveness — nav hamburger + primary-path fixes

The top nav packed brand + health + pipeline chip + ~7 inline links + an
action slot into one flex row, colliding/overflowing on phones (operator:
'almost unusable'). Below 768px the links now fold into a hamburger v-menu;
below 480px the brand text hides (glyph still brands). Plus the primary
browsing path:
- BulkEditorPanel: fixed 320px -> min(320px, 90vw) so it can't swallow the screen.
- GalleryFilterBar: <600px gives search its own full-width row (its 200px
  min-width was jamming the wrapping bar); sort grows.
- GalleryFacetPanel: <480px wraps groups + lets the side-by-side date inputs
  grow full-width.
- ArtistsView grid: minmax(min(440px,100%),1fr) so a card never overflows
  (single column on phones).
- GalleryView: hide the year/month timeline strip <600px.
ImageViewer already stacks its side panel below the image <900px (left as-is).

Secondary surfaces (Posts/Subscriptions filter bars, SubscriptionsTab table,
SeriesReader, PostCard) still need a mobile pass — follow-up.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/components/gallery/BulkEditorPanel.vue

@@ -186,7 +186,9 @@ async function onDeleteConfirm(token) {
 <style scoped>
 .fc-bulk-panel {
   position: fixed; top: 0; right: 0;
-  width: 320px; height: 100vh; z-index: 1100;
+  /* min(320px, 90vw): on phones the panel never swallows the whole screen —
+     leaves a sliver of the gallery visible behind it. */
+  width: min(320px, 90vw); height: 100vh; z-index: 1100;
   background: rgb(var(--v-theme-surface));
   border-left: 1px solid rgb(var(--v-theme-surface-light));
   box-shadow: -2px 0 16px rgba(0, 0, 0, 0.4);

frontend/src/components/gallery/GalleryFacetPanel.vue

@@ -143,4 +143,11 @@ onBeforeUnmount(() => { if (debounce) clearTimeout(debounce) })
 .fc-facets__empty { color: rgb(var(--v-theme-on-surface-variant)); font-size: 0.8rem; }
 .fc-facets__date { max-width: 160px; }
 .fc-facets__dash { color: rgb(var(--v-theme-on-surface-variant)); }
+
+/* Phones: let each facet group wrap and the side-by-side date inputs grow to
+   full width so they don't overflow a ~360px viewport. */
+@media (max-width: 480px) {
+  .fc-facets__group { flex-wrap: wrap; }
+  .fc-facets__date { max-width: none; flex: 1 1 9rem; }
+}
 </style>

frontend/src/components/gallery/GalleryFilterBar.vue

@@ -258,4 +258,12 @@ function pushFilter(mutate) {
 .fc-filterbar__search { max-width: 320px; min-width: 200px; }
 .fc-filterbar__chips { display: flex; align-items: center; gap: 6px; flex-wrap: wrap; }
 .fc-filterbar__sort { max-width: 150px; }
+
+/* Phones: the search's 200px min-width jams the wrapping bar. Give search its
+   own full-width row and let sort grow; everything else wraps under it. */
+@media (max-width: 600px) {
+  .fc-filterbar { gap: 8px; }
+  .fc-filterbar__search { min-width: 100%; max-width: none; }
+  .fc-filterbar__sort { max-width: none; flex: 1 1 auto; }
+}
 </style>