修复：调整游客取号限流策略

问题：移动网络共享出口 IP 会造成游客取号被误限流。

实现：移除公开取号 IP 限制，改用项目总量与手机号 HMAC 限流，并支持 Retry-After 倒计时。

server/README.md

@@ -51,7 +51,11 @@ self-service, including each project's allowed party-size range.
 `POST /api/public/projects/{id}/tickets` uses the same ticket
 validation, queue locking and idempotency rules as the staff ticket flow, but
 returns only the public ticket projection and a private status token. Public
-ticket creation is rate-limited and audited as `PUBLIC_TICKET_CREATED`.
+ticket creation is rate-limited per project and per normalized phone HMAC, and
+audited as `PUBLIC_TICKET_CREATED`. The default limits are 1000 project requests
+and 5 requests for the same project/phone in one minute; configure them with
+`PUBLIC_TICKET_PROJECT_LIMIT`, `PUBLIC_TICKET_PHONE_LIMIT` and
+`PUBLIC_TICKET_RATE_WINDOW`. Ticket creation does not reject by client IP.
 
 `POST /api/public/status/search` is a temporary non-production operational-test
 endpoint. It accepts `{ "phone": "..." }` and returns all current active