feat(billing-feature): introduce billing module with Money class, calculation logic, and DI setup

- Added `Money` value class for precise monetary operations.
- Implemented `BillingCalculator` to handle fee calculations, including ÖTO-compliant contributions and prize distribution rules.
- Created `BillingModule` for dependency injection using Koin.
- Integrated `billing-feature` into the desktop shell and project dependencies.
- Introduced `TurnierWizardV2` and `VeranstalterAuswahlV2` screens with improved UI and billing synchronization support.

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

frontend/features/billing-feature/build.gradle.kts

@@ -0,0 +1,47 @@
+/**
+ * Dieses Modul kapselt die Gebühren-Logik und Abrechnungs-Features (Billing-Sync).
+ */
+plugins {
+  alias(libs.plugins.kotlinMultiplatform)
+  alias(libs.plugins.composeMultiplatform)
+  alias(libs.plugins.composeCompiler)
+  alias(libs.plugins.kotlinSerialization)
+}
+
+group = "at.mocode.clients"
+version = "1.0.0"
+
+kotlin {
+  jvm()
+
+  sourceSets {
+    commonMain.dependencies {
+      implementation(projects.frontend.core.designSystem)
+      implementation(projects.frontend.core.network)
+      implementation(projects.frontend.core.domain)
+      implementation(projects.core.coreDomain)
+
+      implementation(compose.foundation)
+      implementation(compose.runtime)
+      implementation(compose.material3)
+      implementation(compose.ui)
+      implementation(compose.components.resources)
+      implementation(compose.materialIconsExtended)
+
+      implementation(libs.bundles.kmp.common)
+      implementation(libs.bundles.compose.common)
+
+      implementation(libs.koin.core)
+      implementation(libs.koin.compose)
+    }
+
+    commonTest.dependencies {
+      implementation(libs.kotlin.test)
+      implementation(libs.kotlinx.coroutines.test)
+    }
+
+    jvmMain.dependencies {
+      implementation(compose.uiTooling)
+    }
+  }
+}