fix: neighbor UI — show neighbors crash, dark mode contrast (#523) (#527)

## Summary

Part of #523 — fixes bugs 5 and 7 (bug 6 was a duplicate of bug 7).

### Bug 5: Show Neighbors button throws `window._mapSelectRefNode is not
a function`

**Root cause:** Map popup HTML used inline `onclick` calling
`window._mapSelectRefNode`, which was deleted on SPA page destroy. If a
popup persisted after navigation, clicks would throw.

**Fix:** Replaced inline `onclick` with event delegation. A
document-level click handler catches all `[data-show-neighbors]` clicks
and calls `selectReferenceNode` directly. The global
`window._mapSelectRefNode` is still exposed for existing Playwright
tests but is no longer relied upon by the UI.

### Bug 7: Blue text on dark blue background (dark mode contrast)

**Root cause:** Neighbor table cells inside `.node-detail-section` /
`.node-full-card` inherited accent/link color instead of using
`var(--text)`, making text unreadable in dark mode.

**Fix:** Added explicit `color: var(--text)` on `.node-detail-section
.data-table td` and `.node-full-card .data-table td`. Only `<a>` tags
within those cells retain `color: var(--accent)`.

### Files changed
- `public/map.js` — event delegation for Show Neighbors
- `public/style.css` — contrast fix for neighbor table cells

---------

Co-authored-by: you <you@example.com>

public/map.js

@@ -807,7 +807,15 @@
     if (cb) cb.checked = true;
     renderMarkers();
   }
-  // Expose for popup onclick and testing
+  // Event delegation for Show Neighbors links (avoids inline onclick / global function timing issues)
+  document.addEventListener('click', function(e) {
+    var link = e.target.closest('[data-show-neighbors]');
+    if (link) {
+      e.preventDefault();
+      selectReferenceNode(link.dataset.pubkey, link.dataset.name);
+    }
+  });
+  // Expose for testing
   window._mapSelectRefNode = selectReferenceNode;
   window._mapGetNeighborPubkeys = function() { return neighborPubkeys ? Array.from(neighborPubkeys) : []; };
 
@@ -838,7 +846,7 @@
         </dl>
         <div style="margin-top:8px;clear:both;">
           <a href="#/nodes/${node.public_key}" style="color:var(--accent);font-size:12px;">View Node →</a>
-          ${node.public_key ? ` · <a href="#" onclick="event.preventDefault();window._mapSelectRefNode('${safeEsc(node.public_key.replace(/\\/g, '\\\\').replace(/'/g, "\\'").replace(/</g, '\\x3c'))}','${safeEsc((node.name || 'Unknown').replace(/\\/g, '\\\\').replace(/'/g, "\\'").replace(/</g, '\\x3c'))}')" style="color:var(--accent);font-size:12px;">Show Neighbors</a>` : ''}
+          ${node.public_key ? ` · <a href="#" data-show-neighbors data-pubkey="${escapeHtml(node.public_key)}" data-name="${escapeHtml(node.name || 'Unknown')}" style="color:var(--accent);font-size:12px;">Show Neighbors</a>` : ''}
         </div>
       </div>`;
   }

public/style.css

@@ -630,6 +630,15 @@ button.ch-item.selected { background: var(--selected-bg); }
   background: var(--card-bg); border: 1px solid var(--border);
   border-radius: 8px; padding: 12px; margin-bottom: 8px;
 }
+/* Bug 7 fix: neighbor table text inherits accent color — force readable text */
+.node-detail-section .data-table td,
+.node-full-card .data-table td {
+  color: var(--text);
+}
+.node-detail-section .data-table td a,
+.node-full-card .data-table td a {
+  color: var(--accent);
+}
 .node-detail-section h4 {
   font-size: 12px; text-transform: uppercase; letter-spacing: .5px;
   color: var(--text-muted); margin-bottom: 8px; padding-bottom: 4px;