[gg582]

Summary

• accept named inbound station requests with @request: while preserving existing nine-digit key login
• persist pending requests in ddial_station_requests.dat with atomic rewrites, stable ids, and duplicate suppression
• add operator-only /ddial requests, /ddial approve , and /ddial deny
• reuse station key issuance on approval, remove approved/denied requests, and roll back state on persistence failures
• add eight-language help/messages and DDial documentation

Tests

• make -j2
• make unit-test
• make SANITIZE=address,undefined unit-test
• loopback coverage for request registration, persistence reload, approval key login, denial, duplicate requests, and operator checks