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/book_detail.templ

@@ -9,7 +9,7 @@ import (
 	"strings"
 )
 
-templ BookDetail(user User, book handlers.MediaDetail, errorMessage string) {
+templ BookDetail(user User, book handlers.MediaDetail, errorMessage string, tombstoneDays int) {
 	<!DOCTYPE html>
 	<html lang="en">
 		<head>
@@ -440,7 +440,7 @@ templ BookDetail(user User, book handlers.MediaDetail, errorMessage string) {
 				}
 			</div>
 			@ProgressSyncModal(user, book)
-			@NotesHighlightsModal(user, book)
+			@NotesHighlightsModal(user, book, tombstoneDays)
 			@AnnotationsBanner(book)
 			if user.Role == "admin" {
 				@MetadataEditorModal(book)