Badge emblems, profile social links, and SEO/OG social previews

- Achievement badge share-image now draws a milestone emblem (⚡🎯⭐🏆) in the medal
- Profile: Facebook/X/YouTube/Instagram/TikTok/Telegram/LinkedIn/Website links, shown on the public bio page
- OG + Twitter Card tags on homepage/ledger/contract (hero banner as share image)
- Per-member OG tags server-injected into /wall/<username> so shared bio links preview with name/bio/avatar
- robots.txt + sitemap.xml; .txt/.xml MIME types

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

public/assets/wall.js

@@ -18,6 +18,14 @@
   if (w.avatarUrl) { const av = IAP.$('bioAvatar'); av.src = w.avatarUrl; av.hidden = false; }
   IAP.$('bioText').textContent = w.bio || 'Building a team on InstantAdPay — join through this page and you\'re in my line.';
   if (w.qrUrl) IAP.$('bioQr').src = w.qrUrl;
+  // social links
+  const SOC = { facebook: 'Facebook', twitter: 'X', youtube: 'YouTube', instagram: 'Instagram', tiktok: 'TikTok', telegram: 'Telegram', linkedin: 'LinkedIn', website: 'Website' };
+  const sc = IAP.$('bioSocials');
+  if (sc && w.socials && typeof w.socials === 'object') {
+    const links = Object.keys(SOC).filter(k => w.socials[k]).map(k =>
+      '<a href="' + String(w.socials[k]).replace(/"/g, '%22') + '" target="_blank" rel="noopener nofollow me">' + SOC[k] + '</a>');
+    sc.innerHTML = links.join('');
+  }
   IAP.$('wallCtaHead').textContent = 'Join ' + w.name + '’s line';
   IAP.$('wallJoin').href = w.joinUrl;
   // per-wall viewed-position memory (survives revisits; anonymous-friendly)