Improve Twitter/X link handling and text formatting

- Use FxTwitter API for full note tweet text (with syndication API fallback)
- Save Twitter posts based on media content:
  - Videos → embed type (proxied video)
  - Images → image type (gallery)
  - Text-only → quote type
- Add granular preview badges: 'X VIDEO', 'X GALLERY', 'X POST'
- Preserve formatting/spacing with white-space: pre-wrap for quotes and descriptions
- Rename VideoInfo to EmbedInfo for better semantic clarity

internal/static/js/app.js

@@ -183,7 +183,17 @@ async function fetchPreview(url) {
       html += `<div class="preview-description">${escapeHtml(data.description)}</div>`;
     }
     if (data.isEmbed) {
-      html += `<div class="preview-badge">${escapeHtml(data.provider.toUpperCase())} VIDEO</div>`;
+      let badge = data.provider.toUpperCase() + ' VIDEO';
+      if (data.provider === 'twitter') {
+        if (data.mediaType === 'video') {
+          badge = 'X VIDEO';
+        } else if (data.mediaType === 'images') {
+          badge = 'X GALLERY';
+        } else {
+          badge = 'X POST';
+        }
+      }
+      html += `<div class="preview-badge">${escapeHtml(badge)}</div>`;
     }
 
     preview.innerHTML = html || "<div>No preview available</div>";