Two gateway fixes:
1. MessageDeduplicator.is_duplicate() now checks TTL at query time (#10306)
Previously, is_duplicate() returned True for any previously seen ID
without checking its age — expired entries were only purged when cache
size exceeded max_size. On normal workloads that never overflow, message
IDs stayed deduplicated forever instead of expiring after the TTL.
Fix: check `now - timestamp < ttl` before returning True. Expired
entries are removed and treated as new messages.
2. Gateway --config flag now uses yaml.safe_load() (#10216)
The --config CLI flag in gateway/run.py main() used json.load() to
parse config files. YAML is the only documented config format and
every other config loader uses yaml.safe_load(). A YAML config file
passed via --config would crash with json.JSONDecodeError.
Closes#10306Closes#10216
