Feature: Play remote audio on iPhone via WebAudio + self-hosted Opus WASM

iOS WebKit lacks Media Source Extensions with WebM/Opus, so remote audio
was silent on iPhone Safari/Chrome even though audio frames kept flowing.
Add a Web Audio API fallback path that decodes Opus packets with the
`opus-decoder` WASM library and schedules them onto an AudioContext.

The decoder bundle is now self-hosted — served at /static/opus-decoder.min.js
by both the Go and C++ servers — instead of pulled from a CDN, which was
unreachable from some networks.

Gotcha fixed during bring-up: the unscoped `opus-decoder` build's
`OpusDecoder.decodeFrame` is synchronous and returns {channelData,
samplesDecoded, sampleRate, errors} directly, not a Promise, so it must be
called in try/catch rather than via .then().

Also remove the on-screen diagnostic overlay (audio toast + frame counter)
used while debugging the phone without a console; diagnostics now go to
console.* only.

Co-Authored-By: deepseek-v4-pro

server/2015Remote/WebService.cpp

@@ -255,6 +255,7 @@ void CWebService::ServerThread(int port) {
     static std::string cachedXtermJs    = LoadBinaryResourceAsString(IDR_WEB_XTERM_JS);
     static std::string cachedXtermCss   = LoadBinaryResourceAsString(IDR_WEB_XTERM_CSS);
     static std::string cachedXtermFitJs = LoadBinaryResourceAsString(IDR_WEB_XTERM_FIT_JS);
+    static std::string cachedOpusDecoderJs = LoadBinaryResourceAsString(IDR_WEB_OPUS_DECODER_JS);
 
     auto buildStatic = [](const std::string& body, const std::string& mime) {
         ws::HttpResponse r = ws::HttpResponse::OK(body, mime);
@@ -274,6 +275,9 @@ void CWebService::ServerThread(int port) {
         } else if (path == "/static/xterm-fit.js") {
             if (cachedXtermFitJs.empty()) return ws::HttpResponse::NotFound();
             return buildStatic(cachedXtermFitJs, "application/javascript; charset=utf-8");
+        } else if (path == "/static/opus-decoder.min.js") {
+            if (cachedOpusDecoderJs.empty()) return ws::HttpResponse::NotFound();
+            return buildStatic(cachedOpusDecoderJs, "application/javascript; charset=utf-8");
         } else if (path == "/health") {
             return ws::HttpResponse::OK("{\"status\":\"ok\"}", "application/json");
         } else if (path == "/manifest.json") {