Add comprehensive account linking functionality to automatically match bank accounts to Firefly III accounts, with manual override options. This includes:
- New LinkStore module for persistent storage of account links with auto-linking based on IBAN matching
- Extended adapter traits with inspection methods (list_accounts, get_account_status, etc.) and discover_accounts for account discovery
- Integration of linking into sync logic to automatically discover and link accounts before syncing transactions
- CLI commands for managing account links (list, create, etc.)
- Updated README with new features and usage examples
This enables users to easily manage account mappings between sources and destinations, reducing manual configuration and improving sync reliability.
