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/settings.py

@@ -2,11 +2,23 @@ import json
 import os
 import binascii
 
+
+def _settings_path():
+    """Path to settings.json in project root (writable without root)."""
+    try:
+        base = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+        return os.path.join(base, "settings.json")
+    except Exception:
+        return "settings.json"
+
+
 class Settings(dict):
-    SETTINGS_FILE = "/settings.json"
+    SETTINGS_FILE = None  # Set in __init__ from _settings_path()
 
     def __init__(self):
         super().__init__()
+        if Settings.SETTINGS_FILE is None:
+            Settings.SETTINGS_FILE = _settings_path()
         self.load()  # Load settings from file during initialization
 
     def generate_secret_key(self):