[fix](trx-frontend): fix audio callback parse error

Rename the duplicate callback-local variable so app.js loads cleanly and dependent plugin scripts can access shared helpers.

Co-authored-by: OpenAI Codex <codex@openai.com>
Signed-off-by: Stan Grams <sjg@haxx.space>

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

@@ -2909,10 +2909,10 @@ function startRxAudio() {
         opusDecoder = new AudioDecoder({
           output: (frame) => {
             const frameChannels = extractAudioFrameChannels(frame);
-            const now = Date.now();
-            if (now - lastLevelUpdate >= 50) {
+            const levelNow = Date.now();
+            if (levelNow - lastLevelUpdate >= 50) {
               setAudioLevel(levelFromChannels(frameChannels, frame.numberOfFrames));
-              lastLevelUpdate = now;
+              lastLevelUpdate = levelNow;
             }
             const forceMono = frame.numberOfChannels >= 2
               && wfmAudioModeEl