restructure and add a multicast_frontend

src/auracast/server/multicast_frontend.py

@@ -0,0 +1,52 @@
+# frontend/app.py
+import streamlit as st
+import requests
+
+# Global: desired packetization time in ms for Opus (should match backend)
+PTIME = 40
+BACKEND_URL = "http://localhost:5000"
+
+
+st.title("🎙️ WebRTC mic → backend demo")
+st.markdown("Click start and speak; watch your backend logs to see incoming RTP.")
+
+component = f"""
+<button id='go'>Start microphone</button>
+<script>
+    const go = document.getElementById('go');
+    go.onclick = async () => {{
+    go.disabled = true;
+    const pc = new RTCPeerConnection(); // No STUN needed for localhost
+    const stream = await navigator.mediaDevices.getUserMedia({{audio:true}});
+    stream.getTracks().forEach(t => pc.addTrack(t, stream));
+
+    // --- WebRTC offer/answer exchange ---
+    const offer = await pc.createOffer()
+    // Patch SDP offer to include a=ptime using global PTIME
+    let sdp = offer.sdp;
+    const ptime_line = 'a=ptime:{PTIME}';
+    const maxptime_line = 'a=maxptime:{PTIME}';
+    if (sdp.includes('a=sendrecv')) {{
+        sdp = sdp.replace('a=sendrecv', 'a=sendrecv\\n' + ptime_line + '\\n' + maxptime_line);
+    }} else {{
+        sdp += '\\n' + ptime_line + '\\n' + maxptime_line;
+    }}
+    const patched_offer = new RTCSessionDescription({{sdp, type: offer.type}})
+    await pc.setLocalDescription(patched_offer)
+
+    // Send offer to backend
+    const response = await fetch(
+        "{BACKEND_URL}/offer",
+        {{
+            method: 'POST',
+            headers: {{'Content-Type':'application/json'}},
+            body: JSON.stringify({{sdp: pc.localDescription.sdp, type: pc.localDescription.type}})
+        }}
+    )
+    const answer = await response.json()
+    await pc.setRemoteDescription(new RTCSessionDescription({{sdp: answer.sdp, type: answer.type}}))
+    }};
+</script>
+"""
+st.components.v1.html(component, height=80)
+