Add issue number to card overlay (bottom-left)

Each card frame now shows № 01 at the bottom-left alongside the
existing plate number (top-left) and category (top-right).

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

layouts/index.html

@@ -40,6 +40,7 @@
         </picture>
         <span class="card__num">PLATE №{{ $p.Params.plate }}</span>
         <span class="card__cat">{{ index ($p.Params.categories | default (slice "")) 0 }}</span>
+        <span class="card__issue">№ {{ index ($p.Params.issues | default (slice "01")) 0 }}</span>
       </div>
       <div class="card__meta">
         <h2 class="card__title">{{ $p.Title }}</h2>