Add UDP listener for lip sync amplitude from voice service

Listens on UDP :8782 for bare integer amplitude values (0-100),
forwards directly to Pico serial as fire-and-forget jaw commands.
Runs as daemon thread alongside the HTTP server.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

light_service.py

@@ -15,9 +15,11 @@ API:
   POST /state  - Set state {"state": "listening"}
   POST /jaw/level - Set jaw level {"level": 0-100}
   POST /jaw/mode  - Set jaw mode {"mode": "talking"}
+  UDP  :8782   - Jaw amplitude (bare integer, fire-and-forget lip sync)
 """
 
 import time
+import socket
 import threading
 import json
 import signal
@@ -26,6 +28,7 @@ import serial
 
 # === Configuration ===
 HTTP_PORT = 8781
+UDP_PORT = 8782
 SERIAL_PORT = "/dev/ttyACM0"
 SERIAL_BAUD = 115200
 
@@ -152,6 +155,24 @@ class LightAPIHandler(BaseHTTPRequestHandler):
         self.send_header('Access-Control-Allow-Headers', 'Content-Type')
         self.end_headers()
 
+# === UDP Amplitude Listener ===
+def run_udp_listener():
+    """Listen for jaw amplitude via UDP (fire-and-forget from voice service)."""
+    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+    sock.bind(('0.0.0.0', UDP_PORT))
+    sock.settimeout(1.0)
+    print(f"[LIGHT] UDP listener on port {UDP_PORT}")
+    while running:
+        try:
+            data, _ = sock.recvfrom(16)
+            level = max(0, min(100, int(data)))
+            send_amplitude(level)
+        except socket.timeout:
+            continue
+        except (ValueError, Exception):
+            pass
+    sock.close()
+
 # === Signal Handler ===
 def signal_handler(sig, frame):
     global running
@@ -173,6 +194,10 @@ def main():
     # Set initial mood on Pico
     send_mode_command("mood idle")
 
+    # Start UDP listener for lip sync amplitude
+    udp_thread = threading.Thread(target=run_udp_listener, daemon=True)
+    udp_thread.start()
+
     server = HTTPServer(('0.0.0.0', HTTP_PORT), LightAPIHandler)
     print(f"[LIGHT] HTTP API listening on port {HTTP_PORT}")
     print("[LIGHT] Service ready")