Pi port: serial transport, addressed ESP-NOW bridge, port 80

- Run app on Raspberry Pi: serial to ESP32 bridge at 912000 baud, /dev/ttyS0
- Remove ESP-NOW/MicroPython-only code from src (espnow, p2p, wifi, machine/Pin)
- Transport: always send 6-byte MAC + payload; optional to/destination_mac in API and WebSocket
- Settings and model DB use project paths (no root); fix sys.print_exception for CPython
- Preset/settings controllers use get_current_sender(); template paths for cwd=src
- Pipfile: run from src, PORT from env; scripts for port 80 (setcap) and test
- ESP32 bridge: receive 6-byte addr + payload, LRU peer management (20 max), handle ESP_ERR_ESPNOW_EXIST
- Add esp32/main.py, esp32/benchmark_peers.py, scripts/setup-port80.sh, scripts/test-port80.sh

Made-with: Cursor

src/models/transport.py

@@ -0,0 +1,66 @@
+import asyncio
+import json
+
+
+# Default: broadcast (6 bytes). Pi always sends 6-byte address + payload to ESP32.
+BROADCAST_MAC = bytes.fromhex("ffffffffffff")
+
+
+def _encode_payload(data):
+    if isinstance(data, str):
+        return data.encode()
+    if isinstance(data, dict):
+        return json.dumps(data).encode()
+    return data
+
+
+def _parse_mac(addr):
+    """Convert 12-char hex string or 6-byte bytes to 6-byte MAC."""
+    if addr is None or addr == b"":
+        return BROADCAST_MAC
+    if isinstance(addr, bytes) and len(addr) == 6:
+        return addr
+    if isinstance(addr, str) and len(addr) == 12:
+        return bytes.fromhex(addr)
+    return BROADCAST_MAC
+
+
+async def _to_thread(func, *args):
+    to_thread = getattr(asyncio, "to_thread", None)
+    if to_thread:
+        return await to_thread(func, *args)
+    loop = asyncio.get_event_loop()
+    return await loop.run_in_executor(None, func, *args)
+
+
+class SerialSender:
+    def __init__(self, port, baudrate, default_addr=None):
+        import serial
+
+        self._serial = serial.Serial(port, baudrate=baudrate, timeout=1)
+        self._default_addr = _parse_mac(default_addr)
+
+    async def send(self, data, addr=None):
+        mac = _parse_mac(addr) if addr is not None else self._default_addr
+        payload = _encode_payload(data)
+        await _to_thread(self._serial.write, mac + payload)
+        return True
+
+
+_current_sender = None
+
+
+def set_sender(sender):
+    global _current_sender
+    _current_sender = sender
+
+
+def get_current_sender():
+    return _current_sender
+
+
+def get_sender(settings):
+    port = settings.get("serial_port", "/dev/ttyS0")
+    baudrate = settings.get("serial_baudrate", 912000)
+    default_addr = settings.get("serial_destination_mac", "ffffffffffff")
+    return SerialSender(port, baudrate, default_addr=default_addr)