feat(mongodb-sync): add independent history appenders

[bercianor]

Summary

• Implement independent audit-history and journal-history append operations for MongoDB sync.
• Route historical journal events to the stage selected through the persistence factory, preserving the source payload.
• Preserve backend transaction boundaries and confirm stream sequences only after durable writes.

Testing

• 83 MongoDB sync audit-store tests passed, with no failures or skipped tests.
• Module license checks passed during focused validation.
• Independent static verification found no remaining confirmed blocking issues.
• Full repository build remains pending CI.