Fix audio device: dynamische Kartensuche statt hardcoded plughw:2,0

Nach Neustart wechselt die ALSA-Kartennummer (war 2, ist jetzt 1).
find_audio_device() sucht per /proc/asound/cards nach dem USB-Gerät.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/main.py

@@ -111,17 +111,31 @@ def stream():
 # Minimale Latenz: kein HTTP-Buffering, kein Codec-Delay
 # ---------------------------------------------------------------------------
 
-AUDIO_DEVICE = "plughw:2,0"
 AUDIO_SAMPLERATE = 16000
 AUDIO_CHUNK = 512  # ~32ms bei 16kHz
 
 
+def find_audio_device() -> str:
+    """Findet die USB-Soundkarte dynamisch anhand des Namens."""
+    try:
+        with open("/proc/asound/cards") as f:
+            for line in f:
+                # Zeile mit Kartennummer: " 1 [Device  ]: USB-Audio ..."
+                m = re.match(r"^\s*(\d+)\s+\[.*\].*USB", line)
+                if m:
+                    return f"plughw:{m.group(1)},0"
+    except Exception:
+        pass
+    return "plughw:1,0"  # Fallback
+
+
 @sock.route("/audio-ws")
 def audio_ws(ws):
+    device = find_audio_device()
     process = subprocess.Popen(
         [
             "arecord",
-            "-D", AUDIO_DEVICE,
+            "-D", device,
             "-f", "S16_LE",
             "-r", str(AUDIO_SAMPLERATE),
             "-c", "1",