feat(invoice): add e-invoice support with XRechnung/ZUGFeRD and advanced export features

changelog.md

@@ -5,6 +5,27 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.2.0] - 2025-01-09
+
+### Added
+- **E-Invoice Integration**: Full XRechnung/ZUGFeRD support with import/export capabilities
+- **Invoice Processing**: Automatic booking of electronic invoices to accounting
+- **Advanced Export Features**: Comprehensive export functionality for accounts, balances, and ledger data
+- **PDF Generation**: Professional PDF report generation with customizable templates
+- **Security Features**: Merkle tree audit trails and digital signature support for tamper-proof records
+- **Invoice Storage**: Dedicated invoice persistence layer with search and filtering
+- **Invoice Adapter**: Bidirectional conversion between e-invoice formats and internal data model
+- **Invoice Booking Engine**: Intelligent automatic account detection and VAT splitting
+- **Cryptographic Signatures**: Support for signing exports with private keys and certificates
+- **Structured Export Formats**: Export data in multiple formats (JSON, CSV, PDF)
+- **Jahresabschluss Export**: Complete annual closing package generation
+- New dependencies: @e-invoice-eu/core, @fin.cx/einvoice, merkletreejs, node-forge
+- Enhanced documentation with invoice and export examples
+
+### Changed
+- Updated README with comprehensive documentation of new features
+- Expanded API reference with new invoice and export methods
+
 ## [1.1.0] - 2025-01-09
 
 ### Added