- Add ScanAllPubkeys method to scan SerialPubkey index for all pubkeys
- Count events for each pubkey using the Pubkey index
- Store event counts in CURATING_ACL_EVENT_COUNT_ prefix
- Add NIP-86 "scanpubkeys" API endpoint to trigger the scan
This allows the curation UI to show all existing users in the unclassified
list, even if they had events before curating mode was enabled.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>