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

npmextra.json

@@ -0,0 +1,17 @@
+{
+  "npmci": {
+    "npmGlobalTools": [],
+    "npmAccessLevel": "public"
+  },
+  "gitzone": {
+    "projectType": "npm",
+    "module": {
+      "githost": "code.foss.global",
+      "gitscope": "fin.cx",
+      "gitrepo": "skr",
+      "description": "SKR03 and SKR04 German accounting standards for double-entry bookkeeping",
+      "npmPackagename": "@fin.cx/skr",
+      "license": "MIT"
+    }
+  }
+}