feat(validation): integrate ÖTO/FEI rule validations and centralized validators

- Added `OetoValidators` with live-validation for OEPS numbers, FEI-IDs, license classes, and horse data to align with ÖTO/FEI 2026 standards.
- Expanded `ReiterProfilViewModel` and `PferdProfilViewModel` to include validation states (`ValidationResult`) for enhanced form feedback and dirty state tracking.
- Standardized mock data in `Stores.kt` and `NennungModels.kt` to comply with updated validation rules.
- Created `OetoValidatorsTest` to ensure validation logic accuracy (30 unit tests, all green).
- Updated `build.gradle.kts` to include `kotlin.test` dependency for JVM testing.

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

frontend/features/pferde-feature/src/commonMain/kotlin/at/mocode/frontend/features/pferde/presentation/PferdProfilViewModel.kt

@@ -1,5 +1,7 @@
 package at.mocode.frontend.features.pferde.presentation
 
+import at.mocode.frontend.core.domain.validation.OetoValidators
+import at.mocode.frontend.core.domain.validation.ValidationResult
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.SupervisorJob
@@ -16,9 +18,16 @@ data class PferdProfilState(
   val geburtsjahr: String = "",
   val farbe: String = "",
   val rasse: String = "",
-  val validHints: List<String> = emptyList(),
+  // Validierungsergebnisse (Live-Feedback, ÖTO/FEI Regelwerk)
+  val oepsNummerValidation: ValidationResult = ValidationResult.Ok,
+  val feiIdValidation: ValidationResult = ValidationResult.Ok,
   val dirty: Boolean = false,
-)
+) {
+  /** True wenn kein blockierender Fehler vorliegt (Speichern erlaubt). */
+  val isValid: Boolean
+    get() = listOf(oepsNummerValidation, feiIdValidation)
+      .none { it is ValidationResult.Error }
+}
 
 sealed interface PferdProfilIntent {
   data class Load(val id: String) : PferdProfilIntent
@@ -90,7 +99,13 @@ class PferdProfilViewModel(
   }
 
   private inline fun edit(block: (PferdProfilState) -> PferdProfilState) {
-    reduce { block(it).copy(dirty = true) }
+    reduce { s ->
+      val updated = block(s).copy(dirty = true)
+      updated.copy(
+        oepsNummerValidation = OetoValidators.validateOepsNummer(updated.oepsNummer),
+        feiIdValidation = OetoValidators.validateFeiId(updated.feiId),
+      )
+    }
   }
 
   private inline fun reduce(block: (PferdProfilState) -> PferdProfilState) {