feat: klik na produkt v nahlade otvori jeho editor (harmonika)

- v paneli je otvoreny vzdy len jeden produkt, ostatne su zbalene
- klik na kartu produktu v nahlade vyberie sekciu aj produkt, panel sa
  posunie na jeho editor a karta sa v nahlade zvyrazni
- odkazy v nahlade sa klikom neotvaraju

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/lib/productCard.ts

@@ -302,7 +302,7 @@ export function renderProductCard(p: CardProduct, ctx: CardContext): string {
   const key = cardVisualKey(p, ctx);
   const visual = ctx.mode === 'preview' ? renderVisualPreview(p, ctx, key) : renderVisualExport(p, ctx, key);
   return `
-    <table role="presentation" cellspacing="0" cellpadding="0" border="0" width="100%" height="100%" class="glass-product ${colorClass}" bgcolor="${bg}" style="background-color: ${bg}; border-radius: 16px; box-shadow: 0 4px 15px rgba(0, 0, 0, 0.15); overflow: hidden; height: 100%;">
+    <table ${ctx.mode === 'preview' ? `data-product-id="${escapeHtml(p.id)}" ` : ''}role="presentation" cellspacing="0" cellpadding="0" border="0" width="100%" height="100%" class="glass-product ${colorClass}" bgcolor="${bg}" style="background-color: ${bg}; border-radius: 16px; box-shadow: 0 4px 15px rgba(0, 0, 0, 0.15); overflow: hidden; height: 100%;">
         <tr>
             <td style="padding: 0; line-height: 0; font-size: 0; border-top-left-radius: 16px; border-top-right-radius: 16px;">
                 ${visual}