feat(espnow): Pi bridge client, binary wire, and espnow-sender firmware

Replace serial/Wi-Fi driver transport paths with WebSocket bridge client,
binary espnow_wire delivery, device announce registry, and restructured
espnow-sender (AP + broadcast passthrough). Includes docs and tests.

Co-authored-by: Cursor <cursoragent@cursor.com>

espnow-sender/src/main.py

@@ -0,0 +1,76 @@
+import asyncio
+import time
+
+from microdot import Microdot
+from microdot.websocket import WebSocketError, with_websocket
+
+import aioespnow
+import machine
+import network
+from settings import Settings
+
+
+wdt = machine.WDT(timeout=10000)
+wdt.feed()
+settings = Settings()
+print(settings)
+
+app = Microdot()
+
+ap_if = network.WLAN(network.AP_IF)
+ap_if.active(True)
+ap_if.config(ssid=settings.get("name"), password=settings.get("ap_password"))
+print(ap_if.ifconfig())
+
+sta_if = network.WLAN(network.STA_IF)
+sta_if.active(True)
+print(sta_if.config("channel"))
+
+esp = aioespnow.AIOESPNow()
+esp.active(True)
+esp.add_peer(b"\xff\xff\xff\xff\xff\xff")
+
+clients = set()
+
+@app.route("/ws")
+@with_websocket
+async def ws(request, ws):
+    clients.add(ws)
+    while True:
+        
+        try:
+            raw = await ws.receive()
+        except WebSocketError as err:
+            print(err)
+            break
+        if not raw:
+            break
+        try:
+            await esp.asend(b"\xff\xff\xff\xff\xff\xff", raw)
+            print(raw)
+        except Exception as err:
+            print(err)
+            break
+    ws.close()
+    clients.discard(ws)
+
+async def _espnow_receive_loop():
+    async for host, msg in esp.airecv():
+        print(host, msg)
+        for client in clients:
+            await client.send(msg)
+
+
+async def _wdt_feed_loop():
+    while True:
+        await asyncio.sleep(1)
+        wdt.feed()
+
+async def main():
+    asyncio.create_task(_wdt_feed_loop())    
+    asyncio.create_task(_espnow_receive_loop())
+    await app.start_server(host="0.0.0.0", port=80)
+
+
+if __name__ == "__main__":
+    asyncio.run(main())