偿还 lewan 工程债：模块拆分、默认角色降级与短链收口

将 kuaishou-cloud 大入口拆为 prepare/rebind/probe/refresh 等模块；默认角色仅作诊断；补充兑换状态单测；短链明确只读兼容历史链接。

apps/backend/src/services/short-links/short-link-service.ts

@@ -44,6 +44,11 @@ export async function ensureShortLinkForTarget(
 ): Promise<ShortLinkPayload> {
   const normalizedTargetUrl = normalizeTargetUrl(targetUrl)
   const source = String(options.source || '').trim()
+  if (source === SHORT_LINK_SOURCE_KUAISHOU_FEIFEI_CLAIM) {
+    console.warn(
+      '[short-link] feifei claim 已不再使用 shortLink 作为对外交付；请使用本站 /#/claim/{token} 并在 H5 拼 uid',
+    )
+  }
   const targetUrlHash = hashTargetUrl(normalizedTargetUrl)
   const now = nowIso()
   const expiresAt = options.expiresAt !== undefined