Save and Load Mapping Configuration

Persist account mapping configuration and load it for import workflow.

Note: - Store one active mapping configuration per customer - Configuration includes: QB account ID → Costpoint account code, project code rule per account - Store as JSON or relational structure in database - Include metadata: created/updated timestamps, created by user - Validate completeness: all QB accounts must be mapped before allowing import - API endpoints: GET mapping, POST/PUT mapping - Support versioning for audit trail (optional enhancement) - Load mapping automatically when import workflow starts - Handle case where QB accounts change (new accounts added, accounts removed)

Open questions: - Should we validate that mapped Costpoint accounts still exist when loading? - How to handle QB accounts added after mapping was created?