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

core/core-domain/build.gradle.kts

@@ -0,0 +1,17 @@
+plugins {
+    kotlin("jvm")
+    alias(libs.plugins.kotlin.serialization)
+}
+
+dependencies {
+    api(projects.platform.platformDependencies)
+
+    // UUID handling
+    api("com.benasher44:uuid:0.8.2")
+
+    // Serialization
+    api("org.jetbrains.kotlinx:kotlinx-serialization-json")
+    api("org.jetbrains.kotlinx:kotlinx-datetime")
+
+    testImplementation(projects.platform.platformTesting)
+}