feat: Android download page, analysis retry and a collapsible search

- /android is a public page with the latest APK, the server address to copy
  and three install steps; linked from the sign-in screen and the profile menu
- failed audio analysis can be retried from the library page, which also shows
  the most common error; the analyzer no longer burns attempts on files that
  are missing because the disk is not mounted
- the top bar search folds into a round button and slides open on click, "/"
  or Ctrl+K

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/web/src/pages/admin/library.module.css

@@ -118,6 +118,20 @@
   color: var(--danger);
 }
 
+.retryRow {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 16px;
+}
+
+.errorDetail {
+  display: block;
+  margin-top: 4px;
+  color: var(--text3);
+  word-break: break-word;
+}
+
 .bar {
   height: 6px;
   border-radius: 3px;