feat(web): media browse, global search & trash screens (#141)

- MediaBrowseScreen (/app/media): one parameterized screen for all 9 top-level
  kinds with an in-screen kind switcher, per-kind search box, 100/page paging
- SearchScreen (/app/search): grouped per-kind results with counts + 'See all';
  TopBar search input now navigates here
- TrashScreen (/app/trash): state:FileNotFound results, multi-select + Empty Trash
  via DELETE /api/media-items and /api/maintenance/empty_trash (confirm dialogs)
- Shared media/mediaKinds (icon/label maps, hueOf, duration helpers) + MediaPosterCard;
  ChannelBuilder and CollectionsScreen now reuse the single-source maps (their
  exhaustive Record<LibraryBrowseMediaType> had to cover the 6 new kinds anyway)
- api: search.ts, mediaItems.ts, maintenance.ts (+ URL-assert tests)
- One consolidated 'Browse' nav entry with an in-screen kind switcher instead of
  9 per-kind nav rows (deviation from Blazor's per-kind Media links)
- Nav: Media group gains Browse/Search/Trash; Settings Classic-UI help trimmed

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

web/src/shell.css

@@ -2443,6 +2443,110 @@
   }
 }
 
+/* media browse / search / trash poster grid */
+.ctv-media-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
+  gap: var(--space-6, 12px);
+}
+
+.ctv-media-card {
+  position: relative;
+  border-radius: var(--radius-sm);
+  border: 1px solid var(--border-hairline);
+  background: var(--surface-card);
+  overflow: hidden;
+  transition:
+    border-color 120ms ease,
+    box-shadow 120ms ease;
+}
+
+.ctv-media-card[role='button'] {
+  cursor: pointer;
+}
+
+.ctv-media-card-selected {
+  border-color: var(--action-primary);
+  box-shadow: 0 0 0 1px var(--action-primary);
+}
+
+.ctv-media-card-poster {
+  position: relative;
+  overflow: hidden;
+}
+
+.ctv-media-card-poster img {
+  position: absolute;
+  inset: 0;
+  width: 100%;
+  height: 100%;
+  object-fit: cover;
+}
+
+.ctv-media-card-icon {
+  position: absolute;
+  top: 7px;
+  left: 7px;
+  display: inline-flex;
+  z-index: 1;
+}
+
+.ctv-media-card-check {
+  position: absolute;
+  top: 6px;
+  right: 6px;
+  width: 22px;
+  height: 22px;
+  border-radius: 50%;
+  background: var(--action-primary);
+  color: var(--text-on-accent);
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  font-size: 13px;
+  box-shadow: var(--shadow-sm);
+  z-index: 2;
+}
+
+.ctv-media-card-body {
+  padding: 8px 10px 10px;
+}
+
+.ctv-media-card-title {
+  font: var(--weight-semibold) var(--text-xs) / 1.2 var(--font-sans);
+  color: var(--text-primary);
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.ctv-media-card-meta {
+  margin-top: 3px;
+  font: var(--text-2xs) / 1.2 var(--font-sans);
+  color: var(--text-secondary);
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.ctv-media-section-header {
+  display: flex;
+  align-items: baseline;
+  gap: var(--space-4, 8px);
+  margin: var(--space-7, 16px) 0 var(--space-5, 10px);
+}
+
+.ctv-media-section-header h2 {
+  font: var(--weight-semibold) var(--text-md) / 1.2 var(--font-sans);
+  color: var(--text-primary);
+  margin: 0;
+}
+
+.ctv-media-section-count {
+  font: var(--text-xs) / 1 var(--font-sans);
+  color: var(--text-secondary);
+}
+
 /* lineup */
 .ctv-builder-lineup-list {
   display: flex;