feat(ui): migrate remaining pages to the new shell

Apply the sidebar shell and bold primitives across the rest of the app so
the whole experience shares one visual language:

- Browse/organize: series (keeps stacked-covers/series-card CSS),
  collections (keeps wood-paneling + carousel classes), browse_detail.
- Account/stats: profile + form + modal, progress, analytics (stat-card
  tiles), devices, conflicts (status semantics), queue (status/priority
  badges).
- Admin: admin sidebar restyled with icons, dashboard/users/library/
  processing-issues/settings migrated to .card/.btn/.input primitives.
- Docs/setup/misc: docs (keeps prose/highlight.js), api_explorer, setup
  wizard, unlinked_books, custom_section builder.
- Modals/fragments: collection_modal, collection_rules,
  restore_system_collection_modal, filter_item, book_detail_modals — all
  overlays use --surface-overlay + --shadow-pop.

Every Alpine handler, HTMX attribute, id, name, and data-* is preserved;
only presentation changes.

templates/filter_item.templ

@@ -1,16 +1,14 @@
 package templates
 
-// FilterItem renders a single saved filter item for the list
 templ FilterItem(id string, name string) {
 	<div
-		class="flex items-center justify-between p-2 rounded hover:opacity-80"
-		style="background-color: var(--bg-primary);"
+		class="flex items-center justify-between gap-2 p-2 rounded-lg hover:bg-surface-hover"
 		data-filter-id={ id }
 	>
 		<button
 			data-action="load-filter"
 			@click="loadFilter($event)"
-			class="flex-1 text-left px-2 py-1 rounded"
+			class="flex-1 text-left px-2 py-1 text-sm rounded-lg hover:bg-surface-hover"
 			style="color: var(--text-primary);"
 		>
 			{ name }
@@ -18,11 +16,12 @@ templ FilterItem(id string, name string) {
 		<button
 			data-action="delete-filter"
 			@click="deleteFilter($event)"
-			class="p-1 hover:opacity-70 rounded"
+			class="icon-btn shrink-0"
 			style="color: var(--text-secondary);"
 			title="Delete filter"
+			aria-label="Delete filter"
 		>
-			🗑
+			@Icon("trash", "h-4 w-4")
 		</button>
 	</div>
 }