Add in-app settings menu and fix settings API

Move WiFi and device name configuration into a modal menu, reuse existing settings endpoints, and harden settings serialization and startup for MicroPython.

src/main.py

@@ -25,7 +25,8 @@ async def main(port=80):
     settings = Settings()
     print("Starting")
 
-    network.WLAN(network.STA_IF).active(True)
+    sta = network.WLAN(network.STA_IF)
+    sta.active(True)
 
     # Initialize ESPNow singleton (config + peers)
     esp = ESPNow()