feat(ota): 会话 epoch/通道标识 + BLE 中止命令 + NVS 线程安全

- 新增 ota_channel_t(WiFi/BLE) + m_otaEpoch 会话代次，
  abortCurrentIfEpoch 防止同类型重启后旧 handler 误清新会话
- 同通道再次发起 OTA 时自动中止旧会话并重开
- 统一 prepareGd32Storage(validate+begin+erase+meta)，
  消除 BLE/WiFi 两路径隐式差异
- OtaRelay 拆分子步骤(doRelayPackets/doFinishAndVerify)，
  状态成员私有化消除数据竞争
- Gd32FlashStore NVS 读写加 mutex，metaUpdate 原子化
- BLE OTA 新增 0xFB 中止命令（保持连接）+ 0x20 ABORTED 处理
- HTTP handler 改 per-request buffer 支持并发
- 修复 CRITICAL 状态 RSSI 恢复无法降级的缺陷
- main.cpp 关键任务失败触发看门狗重启
- style.css 增强动画 + prefers-reduced-motion 兼容

main/include/app_config.h

@@ -1,4 +1,4 @@
-/*
+/*
  * app_config.h - 统一配置文件（C++ 版本）
  * ESP32-C3 OTA 中继项目
  *
@@ -59,7 +59,7 @@ inline constexpr uint32_t HTTP_SERVER_STACK_SIZE = 8192;           ///< HTTP 服
 // OTA 配置
 // ============================================================
 inline constexpr size_t  OTA_BLOCK_SIZE         = 8192;
-inline constexpr size_t  OTA_MAX_FIRMWARE_SIZE  = 216 * 1024;  // 216KB，对齐 GD32 APP_MAX_SIZE (0x36000)
+inline constexpr size_t  OTA_MAX_FIRMWARE_SIZE  = 216 * 1024;  // 216KB = 221184B = 0x35F90，固件大小上限
 inline constexpr size_t  GD32_OTA_PACKET_SIZE   = 48;          // GD32 OTA 实际转发包载荷
 inline constexpr uint32_t OTA_POLL_RETRIES      = 40;          // 每包 ACK 轮询次数
 inline constexpr uint32_t OTA_RESEND_RETRIES    = 10;           // 每包重发次数上限
@@ -98,6 +98,7 @@ inline constexpr uint8_t BLE_OTA_CTRL_TRIGGER_GD32  = 0xF7;         ///< BLE 控
 inline constexpr uint8_t BLE_OTA_CTRL_TRIGGER_ESP32 = 0xF8;         ///< BLE 控制命令：触发 ESP32 本机 OTA
 inline constexpr uint8_t BLE_OTA_CTRL_VERIFY_SHA256 = 0xF9;         ///< BLE 控制命令：SHA-256 哈希验证
 inline constexpr uint8_t BLE_OTA_CTRL_RESTART_ESP32 = 0xFA;         ///< BLE 控制命令：重启 ESP32
+inline constexpr uint8_t BLE_OTA_CTRL_ABORT_OTA     = 0xFB;         ///< BLE 控制命令：中止当前 OTA（不断开 BLE）
 inline constexpr uint8_t BLE_OTA_CMD_GD32_DATA  = 0x00;             ///< BLE 数据通道：GD32 固件包标识
 inline constexpr uint8_t BLE_OTA_CMD_ESP32_DATA = 0x01;             ///< BLE 数据通道：ESP32 固件包标识
 inline constexpr size_t      BLE_OTA_CHUNK_PAYLOAD = 480;            ///< BLE 单包数据载荷大小（字节）