新增 affiliate_dash 发货平台客户端与签名(阶段 1)

- 平台配置接入:runtime-config/types/defaults/env-overrides/app-config-keys 增加 affiliateDash
- affiliate-dash 平台客户端:请求签名(§3.1 app_key+body_sha256)、回调验签(§3.2 timingSafeEqual)、
  http-client 封装(超时/错误归一/全链路日志)、订单/交付/钱包/商品接口封装
- 单测 12/12 + 全量 211 通过,真实联调拉取线上商品 33 个验证签名链路
- 新增 affiliate_dash 对接文档 v2(含契约验证结论与深度分析)

apps/backend/src/config/env-overrides.ts

@@ -171,6 +171,17 @@ export const ENV_OVERRIDES: readonly EnvOverride[] = [
     'kuaishouFeifei',
     'productRules',
   ]),
+  stringEnv('AFFILIATE_DASH_BASE_URL', ['platforms', 'affiliateDash', 'baseUrl']),
+  stringEnv('AFFILIATE_DASH_APP_KEY', ['platforms', 'affiliateDash', 'appKey']),
+  stringEnv('AFFILIATE_DASH_APP_SECRET', ['platforms', 'affiliateDash', 'appSecret']),
+  stringEnv('AFFILIATE_DASH_CALLBACK_SECRET', ['platforms', 'affiliateDash', 'callbackSecret']),
+  integerEnv('AFFILIATE_DASH_TIMEOUT_MS', ['platforms', 'affiliateDash', 'timeoutMs']),
+  stringEnv('AFFILIATE_DASH_NOTIFY_URL', ['platforms', 'affiliateDash', 'notifyUrl']),
+  integerEnv('AFFILIATE_DASH_TIMESTAMP_TOLERANCE_SECONDS', [
+    'platforms',
+    'affiliateDash',
+    'timestampToleranceSeconds',
+  ]),
   corsOriginsEnv('CORS_ALLOWED_ORIGINS', ['cors', 'allowedOrigins']),
 ]