feat(core): initial release of SKR03/SKR04 German accounting standards implementation

- Complete implementation of German standard charts of accounts
- SKR03 (Process Structure Principle) for trading/service companies
- SKR04 (Financial Classification Principle) for manufacturing companies
- Double-entry bookkeeping with MongoDB persistence
- Comprehensive reporting suite with DATEV export
- Full TypeScript support and type safety

changelog.md

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+# Changelog
+
+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).
+
+## [1.0.0] - 2025-01-09
+
+### Added
+- Initial release of @fin.cx/skr module
+- Complete SKR03 implementation (Process Structure Principle)
+- Complete SKR04 implementation (Financial Classification Principle)
+- Double-entry bookkeeping validation system
+- MongoDB persistence layer using @push.rocks/smartdata
+- Comprehensive account management (100+ predefined accounts per SKR standard)
+- Transaction posting and reversal capabilities
+- Journal entry support with multiple lines
+- Financial reporting suite:
+  - Trial Balance generation
+  - Income Statement (P&L)
+  - Balance Sheet
+  - General Ledger
+  - Cash Flow Statement
+- DATEV-compatible export formats
+- Full TypeScript support with comprehensive type definitions
+- API layer for external integration
+- CSV import/export functionality
+- VAT handling and cost center tracking
+- Automatic balance calculations
+- Period closing functionality
+- Batch transaction processing
+
+### Technical Features
+- Type-safe database operations
+- Indexed MongoDB collections for performance
+- Transaction atomicity and consistency
+- Comprehensive validation rules
+- 4-digit account number validation
+- Account class hierarchy (0-9)
+- Support for custom accounts
+- Real-time balance updates