feat(topbar): drop search box to reclaim filter-bar space

The search box on the right edge of the filter bar wasn't pulling its
weight — kills it entirely along with the supporting plumbing:

- FilterBar: remove input + Search icon import + local/debounced state
- filterStore: drop `q`, `setQ`, plus all references in INITIAL_FILTERS,
  filtersToParams, hasActiveFilters, snapshotFilters
- usePhotosQuery: stop passing q through filtersToParams
- useFilterUrlSync: drop the `q` URL param read/write
- PhotoThumbnail + PreviewView: remove the search-match banner/chip and
  findSearchMatch helper imports
- Timeline + MemoriesView: stop subscribing to / forwarding the prop
- useKeyboardShortcuts: drop the `/` and Cmd+F focus hotkeys
- KeyboardHints: drop the `/` hint and the now-stale `?` collision note
- delete hooks/useSearchQuery.ts (no callers) and lib/searchMatch.ts

Backend /photos/search endpoint left untouched — no UI reaches it now.

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

frontend/src/components/KeyboardHints.tsx

@@ -65,7 +65,6 @@ function getHints(opts: {
     { key: 'Space', action: 'Preview' },
     { key: 'Tab', action: 'Library panel' },
     { key: 'I', action: 'Info panel' },
-    { key: '/', action: 'Search' },
   ]
 }
 
@@ -81,8 +80,7 @@ export function KeyboardHints() {
     localStorage.setItem(STORAGE_KEY, collapsed ? '1' : '0')
   }, [collapsed])
 
-  // `H` toggles the panel. `?` (shift+/) collides with the global `/`
-  // search shortcut, so we use a plain letter instead.
+  // `H` toggles the panel.
   useHotkeys('h', () => setCollapsed((c) => !c), { preventDefault: true })
 
   const hints = getHints({ selectedCount, currentSection, viewMode })