docs(ble): add ESP-BLE-UART companion guide

Move the OpenCode companion guide into the ble_uart_service example.

Add English and Chinese Markdown guides with image assets.

Keep ESP-BLE-UART naming consistent across the example and bridge tooling.


(cherry picked from commit 926111e721)

Co-authored-by: Zhou Xiao <zhouxiao@espressif.com>

examples/bluetooth/ble_uart_service/main/main.c

@@ -3,7 +3,7 @@
  *
  * SPDX-License-Identifier: Unlicense OR CC0-1.0
  *
- * BLE UART Service example. Backend (NimBLE / Bluedroid) is picked
+ * ESP-BLE-UART example. Backend (NimBLE / Bluedroid) is picked
  * by the host-stack Kconfig at compile time. Whatever the central
  * writes to the RX characteristic is echoed back over TX.
  */