chore(docs, design-system, ping-service): integrate SQLDelight with KMP, refine design-system components, and enhance logging

- Added a comprehensive guide for SQLDelight integration in Kotlin Multiplatform, covering setup for Android, iOS, desktop, and web platforms.
- Introduced `DashboardCard` and `DenseButton` to the design system, focusing on enterprise-grade usability and visual consistency.
- Enhanced `PingViewModel` with structured logging (`LogEntry`) functionality for better debugging and traceability across API calls.
- Updated `AppTheme` with a refined color palette, typography, and shapes to align with enterprise UI standards.
- Extended Koin integration and modularized database setup for smoother dependency injection and code reuse.

frontend/shells/meldestelle-portal/src/commonMain/kotlin/MainApp.kt

@@ -13,12 +13,14 @@ import at.mocode.frontend.core.auth.presentation.LoginViewModel
 import at.mocode.ping.feature.presentation.PingScreen
 import at.mocode.ping.feature.presentation.PingViewModel
 import at.mocode.frontend.core.designsystem.components.AppFooter
+import at.mocode.frontend.core.designsystem.theme.AppTheme
 import org.koin.compose.koinInject
 import org.koin.compose.viewmodel.koinViewModel
 
 @Composable
 fun MainApp() {
-  MaterialTheme {
+  // Wrap the entire app in our centralized AppTheme
+  AppTheme {
     Surface(
       modifier = Modifier.fillMaxSize(),
       color = MaterialTheme.colorScheme.background