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_core.h

@@ -0,0 +1,84 @@
+#pragma once
+
+/**
+ * 通用 BLE 外设核心（无 LVGL 依赖）
+ *
+ * 栈：NimBLE（比 Bluedroid 省 RAM/Flash，后续可与 WiFi 共存）
+ * 服务：Nordic UART Service（NUS）— 手机端 nRF Connect / Serial Bluetooth
+ *       Terminal / LightBlue 等主流 App 开箱即用
+ *
+ * 流程：
+ * 1. ble_core_begin() 初始化 NimBLE + NUS，默认开始广播
+ * 2. 手机连上后写 RX 特征 → 回调 / 收包队列
+ * 3. ble_core_send() 经 TX 特征 Notify 发回手机
+ * 4. loop 里 ble_core_loop() 处理断线后自动重广播
+ */
+
+#include <Arduino.h>
+
+#ifndef BLE_CORE_DEVICE_NAME
+#define BLE_CORE_DEVICE_NAME "CYD-BLE"
+#endif
+
+#ifndef BLE_CORE_RX_QUEUE
+#define BLE_CORE_RX_QUEUE 8
+#endif
+
+#ifndef BLE_CORE_RX_MAX
+#define BLE_CORE_RX_MAX 128
+#endif
+
+/** Nordic UART Service（业界事实标准） */
+#define BLE_NUS_SERVICE_UUID "6E400001-B5A3-F393-E0A9-E50E24DCCA9E"
+#define BLE_NUS_RX_UUID      "6E400002-B5A3-F393-E0A9-E50E24DCCA9E"
+#define BLE_NUS_TX_UUID      "6E400003-B5A3-F393-E0A9-E50E24DCCA9E"
+
+enum BleCoreState : uint8_t {
+  BLE_CORE_IDLE = 0,
+  BLE_CORE_ADVERTISING,
+  BLE_CORE_CONNECTED,
+};
+
+struct BleRxPacket {
+  char data[BLE_CORE_RX_MAX + 1];
+  uint16_t len;
+};
+
+using BleCoreStateCb = void (*)(BleCoreState state, void *user);
+using BleCoreRxCb = void (*)(const uint8_t *data, size_t len, void *user);
+
+void ble_core_set_state_cb(BleCoreStateCb cb, void *user = nullptr);
+void ble_core_set_rx_cb(BleCoreRxCb cb, void *user = nullptr);
+
+/** 初始化栈 + NUS；默认开始广播。返回是否成功。 */
+bool ble_core_begin(const char *device_name = BLE_CORE_DEVICE_NAME);
+
+void ble_core_end();
+
+BleCoreState ble_core_state();
+bool ble_core_is_connected();
+bool ble_core_is_advertising();
+
+const char *ble_core_name();
+String ble_core_address();
+String ble_core_peer_address();
+
+void ble_core_advertise_start();
+void ble_core_advertise_stop();
+
+/** 经 NUS TX Notify 发送；未连接返回 false */
+bool ble_core_send(const uint8_t *data, size_t len);
+bool ble_core_send_str(const char *text);
+
+/** 演示用：收到数据自动 echo 回去（默认开） */
+void ble_core_set_echo(bool on);
+bool ble_core_echo();
+
+/**
+ * 非回调路径取收包（UI 轮询友好）。有包返回 true 并填 out。
+ * 与 ble_core_set_rx_cb 可同时用。
+ */
+bool ble_core_poll_rx(BleRxPacket *out);
+
+/** 每 loop 调用：断线后自动重广播 */
+void ble_core_loop();