refactor(theme): centralize colors and typography in AppColors and AppTypography

- Replaced hardcoded color values in `LightColorScheme` and `DarkColorScheme` with `AppColors`.
- Updated `AppTypography` references in `AppMaterialTypography`.
- Upgraded Kotlin, Compose Multiplatform, and Ktor to latest versions in `libs.versions.toml`.
- Added `uiToolingPreview` dependency in `meldestelle-portal` build script.
- Refactored config loading to include `RequestInit`.

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

frontend/shells/meldestelle-portal/build.gradle.kts

@@ -83,6 +83,7 @@ kotlin {
       implementation(compose.ui)
       implementation(compose.components.resources)
       implementation(compose.materialIconsExtended)
+      implementation(compose.components.uiToolingPreview)
 
       // Bundles
       implementation(libs.bundles.kmp.common)        // Coroutines, Serialization, DateTime

frontend/shells/meldestelle-portal/src/jsMain/kotlin/Config.kt

@@ -2,6 +2,7 @@ import kotlinx.browser.window
 import kotlinx.coroutines.await
 import kotlinx.serialization.Serializable
 import kotlinx.serialization.json.Json
+import org.w3c.fetch.RequestInit
 
 private val AppJson = Json { ignoreUnknownKeys = true }
 
@@ -14,7 +15,7 @@ data class AppConfig(
 suspend fun loadAppConfig(): AppConfig {
     return try {
         // ?_nocache erzwingt einen SW-bypassing Request (SW sieht andere URL → Cache-Miss → Netzwerk)
-        val response = window.fetch("/config.json?_nocache=1").await()
+      val response = window.fetch("/config.json?_nocache=1", RequestInit()).await()
         if (!response.ok) {
             console.warn("[Config] Failed to load config.json, falling back to globalThis")
             return fallbackFromGlobal()