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

ts/index.ts

@@ -0,0 +1,10 @@
+export * from './skr.types.js';
+export * from './skr.classes.account.js';
+export * from './skr.classes.transaction.js';
+export * from './skr.classes.journalentry.js';
+export * from './skr.classes.chartofaccounts.js';
+export * from './skr.classes.ledger.js';
+export * from './skr.classes.reports.js';
+export * from './skr.api.js';
+export * from './skr03.data.js';
+export * from './skr04.data.js';