Add pagination to category, tag, and issue pages (10 per page)

pagerSize set to 10 (5 columns × 2 rows). New pagination partial
renders prev/next links and numbered page buttons. Applied to
_default/list.html (categories + tags) and issues/list.html.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

layouts/issues/list.html

@@ -9,10 +9,12 @@
   <p class="font-serif italic text-[clamp(13px,1vw,16px)] leading-[1.65] text-ink-2 max-w-[55ch] m-0">{{ .Params.description }}</p>
 </section>
 
+{{- $paginator := .Paginate .Pages }}
 <section id="grid" data-density="default"
          class="grid [grid-template-columns:repeat(auto-fill,minmax(220px,1fr))] gap-[var(--gap)] px-[var(--pad)] py-[var(--gap)]">
-  {{- range $i, $p := .Pages }}
+  {{- range $i, $p := $paginator.Pages }}
     {{- partial "card.html" (dict "Page" $p "Index" $i) }}
   {{- end }}
 </section>
+{{- partial "pagination.html" $paginator }}
 {{ end }}