Add CYD BLE foundation with NimBLE Nordic UART.

Reusable ble_core (+ optional LVGL ble_ui), flashable firmware/cyd, aligned with wifitest as a base feature.

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

include/ble_ui.h

@@ -0,0 +1,9 @@
+#pragma once
+
+/**
+ * LVGL 屏上 BLE 状态 UI（依赖 ble_core）
+ * 复用：拷贝 ble_ui.* + 在业务里 ble_ui_create() / ble_ui_tick()
+ */
+
+void ble_ui_create();
+void ble_ui_tick();