[feat](trx-frontend-http): add strongest decoded signal summary to map

Add a new "Strongest decoded signal" section below the existing
"Longest decode paths" section on the map tab, showing the top 5
stations with the highest SNR across the current map history window.
Reuses existing map-qso-card styling with SNR displayed in place of
distance.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Signed-off-by: Stanislaw Grams <stanislawgrams@gmail.com>

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

@@ -782,6 +782,15 @@
         </div>
         <div id="map-qso-summary-list" class="map-qso-summary-list"></div>
       </section>
+      <section class="map-qso-summary" aria-labelledby="map-signal-summary-title">
+        <div class="map-qso-summary-head">
+          <div>
+            <div id="map-signal-summary-title" class="map-qso-summary-title">Strongest decoded signal</div>
+            <div class="map-qso-summary-subtitle">Top 5 strongest signals in the current map history</div>
+          </div>
+        </div>
+        <div id="map-signal-summary-list" class="map-qso-summary-list"></div>
+      </section>
     </div>
     <div id="tab-settings" class="tab-panel" style="display:none;">
       <div class="sub-tab-bar">