[fix](trx-frontend-http): buffer decode messages until map-data plugins are ready

Eagerly load map-data plugins (AIS, APRS, VDES, HF-APRS) on startup and
buffer any decode history or live SSE messages that arrive before plugin
handlers register. Each plugin drains its pending buffer on init.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Stan Grams <sjg@haxx.space>

src/trx-client/trx-frontend/trx-frontend-http/assets/web/index.html

@@ -1620,6 +1620,7 @@
 (function() {
   var pluginScripts = {
     'digital-modes': ['/ft8.js', '/ft4.js', '/ft2.js', '/wspr.js', '/cw.js', '/background-decode.js', '/sat.js', '/wefax.js'],
+    'map-data': ['/map-core.js', '/ais.js', '/vdes.js', '/aprs.js', '/hf-aprs.js'],
     'map': ['/map-core.js', '/leaflet-ais-tracksymbol.js', '/ais.js', '/vdes.js', '/aprs.js', '/hf-aprs.js', '/sat.js', '/sat-scheduler.js'],
     'statistics': ['/map-core.js'],
     'bookmarks': ['/bookmarks.js'],
@@ -1639,8 +1640,12 @@
       document.body.appendChild(s);
     });
   }
-  // Load core plugins immediately (needed on main tab)
-  ['digital-modes', 'bookmarks', 'settings'].forEach(loadPlugins);
+  // Load core plugins immediately (needed on main tab).
+  // 'map-data' loads map-core.js + data handlers (ais/aprs/vdes/hf-aprs) eagerly
+  // so decode history replay can populate map data structures before the map
+  // tab is opened.  The 'loaded' Set prevents double-loading when the map tab
+  // is later activated.
+  ['digital-modes', 'map-data', 'bookmarks', 'settings'].forEach(loadPlugins);
   // Load others on tab switch
   document.addEventListener('click', function(e) {
     var tab = e.target.closest('[data-tab]');