refactor: Migrate from monolithic to modular architecture

- Restructure project into domain-specific modules (core, masterdata, members, horses, events, infrastructure)
- Create shared client components in common-ui module
- Implement CI/CD workflows with GitHub Actions
- Consolidate documentation in docs directory
- Remove deprecated modules and documentation files
- Add cleanup and migration scripts for transition
- Update README with new project structure and setup instructions

.github/workflows/build.yml

@@ -0,0 +1,27 @@
+name: Build
+
+on:
+  push:
+    branches: [ main, develop ]
+  pull_request:
+    branches: [ main, develop ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: Set up JDK 21
+      uses: actions/setup-java@v3
+      with:
+        java-version: 21
+        distribution: 'temurin'
+        cache: gradle
+
+    - name: Grant execute permission for gradlew
+      run: chmod +x gradlew
+
+    - name: Build with Gradle
+      run: ./gradlew build