[fix](trx-frontend-http): drop bidirectional requirement for decode paths

The bidirectional check required both A→B and B→A directed messages to
draw a contact line, which was too strict — the receiver may not hear
both sides of a QSO. Now a decode path is drawn whenever a directed
message is decoded and the target's locator is known from any message
in the 24 h history window.

Also rename "Longest QSOs" → "Longest decode paths" and update
related UI labels to better reflect what is actually shown.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Signed-off-by: Stan Grams <sjg@haxx.space>

src/trx-client/trx-frontend/trx-frontend-http/assets/web/app.js

@@ -6319,11 +6319,7 @@ function rebuildDecodeContactPaths() {
       }
     }
   }
-  // Index directed messages by "SOURCE::TARGET" for QSO (bidirectional) check
-  const directedPairs = new Set(directedMessages.map((m) => `${m.source}::${m.target}`));
   for (const msg of directedMessages) {
-    // A true QSO requires both A→B and B→A directed messages
-    if (!directedPairs.has(`${msg.target}::${msg.source}`)) continue;
     const targetLocator = stationLocators.get(msg.target);
     if (!targetLocator) continue;
     if (msg.sourceGrid === targetLocator.grid) continue;