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/shells/meldestelle-desktop/build.gradle.kts

@@ -35,6 +35,7 @@ kotlin {
       implementation(projects.frontend.features.veranstaltungFeature)
       implementation(projects.frontend.features.turnierFeature)
       implementation(project(":frontend:features:profile-feature"))
+      implementation(project(":frontend:features:billing-feature"))
 
       // Compose Desktop
       implementation(compose.desktop.currentOs)