feat: pair controllers and show them in the app

Port the MT76 client functions (send_wlan, associate_client,
pair_client, set_client_key, remove_client) and wire the RX dispatch
into the session: EP IN frames are parsed, ASSOC_REQ associates a
controller (WCID plus chip programming), PAIR_REQ replies with
PAIR_RESP, and DISASSOC or client-lost removes it. The C API exposes
connected controllers and the app lists them by MAC. Bumps
xone_cli/xone_app to C++23: they were falling back to the default
standard once mt76.hpp started using std::span. Adds a unit test pinning
the WCID regions, the 32-byte rxwi, and the new frame control values.

Co-Authored-By: qwen3.8-27b@q2_k_xl: client functions, RX dispatch, GUI list

include/app/xone_api.h

@@ -65,6 +65,13 @@ const char *xone_mac_address(const xone_dongle *d);
 // Empty string if the firmware was not loaded. Valid until xone_close().
 const char *xone_firmware_build(const xone_dongle *d);
 
+// Number of connected controllers.
+int xone_controller_count(xone_dongle const *d);
+
+// Copy the controller at index into buf as "xx:xx:xx:xx:xx:xx". Returns 0 on
+// success, -1 if index is out of range.
+int xone_controller_mac(xone_dongle const *d, int index, char *buf, int len);
+
 #ifdef __cplusplus
 }
 #endif