[fix](trx-frontend-http): dismiss decode history overlay on connection error

decodeSource.onerror terminated the history worker but never called
flushLiveBuffer(), leaving historySettled=false and the "Loading decode
history…" overlay stuck on screen when trx-client breaks.  Call
flushLiveBuffer() in the error path so the overlay is dismissed and the
powerHint connection-lost message is visible to the user.

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/app.js

@@ -7742,6 +7742,7 @@ function connectDecode() {
     decodeSource.close();
     decodeConnected = false;
     terminateDecodeHistoryWorker();
+    if (!historySettled) flushLiveBuffer();
     if (wasClosed) {
       updateDecodeStatus("Decode not available (check client audio config)");
       setTimeout(connectDecode, 10000);