feat(sdk): OTA 升级流程对齐 expo + 拆 extension 文件分层 + 秘钥本地化

主要改动：
- 新增 fetchLatestFirmware/upgradeFirmware/tryReportPendingUpgrade
  三段 OTA 接口，对齐 expo bindDeviceWithOrchestration 行为
- bind 仅做硬绑+getVersion，软绑/对账上报/拉最新固件搬到
  fetchLatestFirmware 内部串；软绑失败自动硬解回滚
- UpgradeRecord 复合主键 (sn, firmwareId) 持久化 + sn 级 in-flight 互斥
- DuooomiBleSDKDelegate 新增 didUpdateUpgradeRecords，集成方
  可观察对账上报结果（reported/outcome 状态）
- DuooomiBleSDK 主类按职责拆 5 个 extension 文件，公开 API 不变
- TargetFirmware 简化为只取必要字段 + 新增 forceUpgrade
- scanNamePrefix 改为必填 String
- demo 秘钥移至本地 DemoSecrets.swift (gitignored)
- README 重写：完整 OTA 流程示例 + 上报状态判定表

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Sources/DuooomiBleSDK/DuooomiBleSDK+Binding.swift

@@ -0,0 +1,109 @@
+import Foundation
+
+// MARK: - Binding (BLE 协议层硬绑/硬解 + 解绑端的软解；OTA 检查/对账/软绑搬到 +Firmware)
+
+extension DuooomiBleSDK {
+
+    /// 硬绑：BLE 协议层把当前用户绑定到设备（命令 0x0F），完成后同步拉一次版本号。
+    ///
+    /// **作用域**：只做 BLE 通道的绑定 + `getDeviceVersion`。
+    /// 软绑 / 升级对账上报 / 拉最新固件 → 全部移到 `fetchLatestFirmware(sn:currentVersion:userId:)` 内部串。
+    ///
+    /// 完成后 SDK 状态变化：
+    /// - `sdk.sn` 写入设备序列号
+    /// - `sdk.version` 写入当前固件版本（getVersion 失败时保持空，但 bind 不算失败）
+    /// - `sdk.isActivated = true`，delegate `didChangeActivation(true)` 回调
+    ///
+    /// - Parameters:
+    ///   - userId: 当前用户 ID（写入 BLE BIND payload 的 `bindUserId` 字段，不依赖登录态 token）
+    ///   - completion: 回调 `Result<BindingResponse, Error>`
+    ///     - 成功：`BindingResponse(success: 1, sn, contents)`
+    ///     - 失败：`.notConnected` / `.alreadyBoundByOtherUser`(success≠1) / `.timeout(.bindDevice)`
+    /// - Note: `bind` / `unbind` / `setPlayMode` 共享 `0x0F` / `0x12` opId 通道，**不能并发**。
+    public func bind(userId: String, completion: @escaping (Result<BindingResponse, Error>) -> Void) {
+        guard ensureConnected(completion: completion) else { return }
+        BleLog.d("Sending bind (userId=\(userId))", "Command")
+
+        sendAsyncAndWait(commandType: .bindDevice, completion: { [weak self] result in
+            guard let self = self else { return }
+            switch result {
+            case .failure(let error):
+                completion(.failure(error))
+            case .success(let data):
+                do {
+                    let resp = try self.decodeResponse(BindingResponse.self, from: data)
+                    self.isActivated = resp.success == 1
+                    if resp.success != 1 {
+                        BleLog.w("Hard bind failed: success=0", "Command")
+                        completion(.failure(DuooomiBleError.alreadyBoundByOtherUser))
+                        return
+                    }
+                    self.sn = resp.sn
+                    BleLog.i("Hard bind success: sn=\(resp.sn)", "Command")
+                    // 同步拉版本，让后续 fetchLatestFirmware 的对账上报有 currentVersion 可用
+                    self.getVersion { _ in
+                        completion(.success(resp))
+                    }
+                } catch {
+                    completion(.failure(error))
+                }
+            }
+        }, send: { done in
+            self.deviceInfoService.bindDevice(userId: userId, completion: done)
+        })
+    }
+
+    /// 解绑：硬解绑（BLE 0x12）→ 软解绑（shipment-sn HTTP）。SDK 内部完成全套。
+    ///
+    /// 软解失败仅打 warn 不阻断硬解结果回传——对端云记录如果残留，由后续 bind 自然修正。
+    ///
+    /// 完成后 SDK 状态变化：
+    /// - `sdk.sn` 清空
+    /// - `sdk.isActivated = false`，delegate `didChangeActivation(false)` 回调
+    ///
+    /// - Parameters:
+    ///   - userId: 当前用户 ID（写入 BLE UNBIND payload + 软解请求体的 `bindUserId`）
+    ///   - completion: 回调 `Result<UnbindResponse, Error>`
+    ///     - 成功：`UnbindResponse(success: 1)`（软解失败也算成功）
+    ///     - 失败：`.notConnected` / `.unbindFailed`(BLE 层 success≠1) / `.timeout(.unbindDevice)`
+    /// - Note: `bind` / `unbind` / `setPlayMode` 共享 `0x0F` / `0x12` opId 通道，**不能并发**。
+    public func unbind(userId: String, completion: @escaping (Result<UnbindResponse, Error>) -> Void) {
+        guard ensureConnected(completion: completion) else { return }
+        let cachedSn = self.sn
+        BleLog.d("Sending unbind (userId=\(userId))", "Command")
+
+        sendAsyncAndWait(commandType: .unbindDevice, completion: { [weak self] result in
+            guard let self = self else { return }
+            switch result {
+            case .failure(let error):
+                completion(.failure(error))
+            case .success(let data):
+                do {
+                    let resp = try self.decodeResponse(UnbindResponse.self, from: data)
+                    if resp.success == 1 {
+                        self.isActivated = false
+                        self.sn = ""
+                        BleLog.i("Hard unbind success", "Command")
+                        if !cachedSn.isEmpty {
+                            self.shipmentService.unbind(sn: cachedSn, bindUserId: userId) { softResult in
+                                if case .failure(let err) = softResult {
+                                    BleLog.w("Soft unbind failed (ignored): \(err.localizedDescription)", "Command")
+                                }
+                                completion(.success(resp))
+                            }
+                        } else {
+                            completion(.success(resp))
+                        }
+                    } else {
+                        BleLog.w("Unbind failed", "Command")
+                        completion(.failure(DuooomiBleError.unbindFailed))
+                    }
+                } catch {
+                    completion(.failure(error))
+                }
+            }
+        }, send: { done in
+            self.deviceInfoService.unbindDevice(userId: userId, completion: done)
+        })
+    }
+}