Add peer-to-peer synchronization for Dolt-backed beads databases:
- New FederatedStorage interface with PushTo, PullFrom, Fetch, ListRemotes,
RemoveRemote, and SyncStatus methods
- DoltStore implementation using DOLT_PUSH, DOLT_PULL, DOLT_FETCH
- Full bd federation command with subcommands:
- sync: bidirectional sync with conflict resolution (--strategy ours|theirs)
- status: show ahead/behind counts and conflict state
- add-peer/remove-peer/list-peers: manage federation remotes
- Comprehensive tests for all federation APIs
Closes: bd-wkumz.4
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>