fix(web): banner highlight delete; retention wording states the days

The book-detail banner's highlight rows gain Delete (tombstoned
server-side, restorable from the Deleted modal — same as the reader
drawers already offered). The deleted-annotations modal now says the
retention in plain language — 'kept for 30 days' from the
annotation_tombstone_ttl_days tunable (threaded through BookDetail →
NotesHighlightsModal; 1-day singular and retention-disabled variants
handled) — instead of referencing a settings name a reader cannot see.

templates/annotations_banner.templ

@@ -99,8 +99,7 @@ templ AnnotationsBanner(book handlers.MediaDetail) {
 								></button>
 								<button
 									type="button"
-									x-show="row.kind === 'note'"
-									@click="deleteBannerNote(row)"
+									@click="row.kind === 'note' ? deleteBannerNote(row) : deleteBannerHighlight(row)"
 									class="text-xs px-2 py-1 rounded-lg hover:bg-surface-hover"
 									style="color: var(--status-danger);"
 								>✕ Delete</button>