chore: remove deprecated horses, clubs, officials, and persons services

- Deleted obsolete modules related to horses, clubs, officials, and persons services, including their configurations, build files, and database provisioning scripts.
- Cleaned up associated references in the project structure (e.g., `settings.gradle.kts`).
- Removed unused database tables and Spring beans related to these domains.

Signed-off-by: Stefan Mogeritsch <stefan.mo.co@gmail.com>

backend/services/identity/identity-domain/build.gradle.kts

@@ -0,0 +1,13 @@
+plugins {
+  alias(libs.plugins.kotlinJvm)
+  alias(libs.plugins.kotlinSerialization)
+}
+
+dependencies {
+  implementation(projects.platform.platformDependencies)
+  implementation(projects.core.coreDomain)
+
+  testImplementation(projects.platform.platformTesting)
+  testImplementation(libs.mockk)
+  testImplementation(libs.kotlin.test)
+}