chore(turnier-feature): remove unused ViewModels and UI components

- Removed `AbteilungViewModel`, `BewerbAnlegenViewModel`, `BewerbViewModel`, and `CreateBewerbWizardScreen`.
- Cleaned up related imports and unused domain models.

frontend/core/auth/build.gradle.kts

@@ -10,13 +10,11 @@ version = "1.0.0"
 
 kotlin {
   jvm()
-  js {
-    binaries.library()
-    browser {
-      testTask {
-        enabled = false
-      }
-    }
+  js(IR) {
+    browser()
+  }
+  wasmJs {
+    browser()
   }
 
   sourceSets {
@@ -63,6 +61,11 @@ kotlin {
       implementation(libs.ktor.client.cio)
     }
 
+    wasmJsMain.dependencies {
+      implementation("org.jetbrains.kotlin:kotlin-stdlib-wasm-js:2.3.20")
+      implementation(libs.ktor.client.js)
+    }
+
     jsMain.dependencies {
       implementation(libs.ktor.client.js)
     }

frontend/core/auth/src/wasmJsMain/kotlin/at/mocode/frontend/core/auth/data/OidcCallback.wasmJs.kt

@@ -0,0 +1,76 @@
+package at.mocode.frontend.core.auth.data
+
+/**
+ * Wasm-Implementierung für OIDC Redirect.
+ */
+actual suspend fun launchOidcFlow(
+  authUrl: String,
+  callbackPort: Int
+): OidcCallbackResult {
+  setWindowLocationHref(authUrl)
+  return OidcCallbackResult.Redirecting
+}
+
+@OptIn(ExperimentalWasmJsInterop::class)
+private fun setWindowLocationHref(url: String): Unit = js("window.location.href = url")
+
+/**
+ * Prüft auf OIDC Callback-Parameter in der URL.
+ */
+actual fun consumePendingOidcCallback(): OidcCallbackResult? {
+  val search: String = getWindowLocationSearch()
+  if (!search.contains("code=")) return null
+
+  val query = search.removePrefix("?")
+  val params = parseQueryParams(query)
+
+  val code = params["code"] ?: return null
+  val state = params["state"] ?: return null
+  val error = params["error"]
+
+  try {
+    replaceWindowState(getWindowLocationPathname())
+  } catch (_: Throwable) {}
+
+  return if (error != null) {
+    OidcCallbackResult.Error(
+      error = error,
+      description = params["error_description"]
+    )
+  } else {
+    OidcCallbackResult.Success(code = code, state = state)
+  }
+}
+
+@OptIn(ExperimentalWasmJsInterop::class)
+private fun getWindowLocationSearch(): String = js("window.location.search")
+@OptIn(ExperimentalWasmJsInterop::class)
+private fun getWindowLocationPathname(): String = js("window.location.pathname")
+@OptIn(ExperimentalWasmJsInterop::class)
+private fun replaceWindowState(path: String): Unit = js("window.history.replaceState(null, '', path)")
+
+private fun parseQueryParams(query: String): Map<String, String> =
+  query.split("&")
+    .filter { it.contains("=") }
+    .associate {
+      val parts = it.split("=", limit = 2)
+      val key = parts[0]
+      val value = decodeURIComponent(parts.getOrElse(1) { "" })
+      key to value
+    }
+
+actual fun getOidcRedirectUri(): String {
+  val origin: String = try {
+    getWindowLocationOrigin()
+  } catch (_: Throwable) {
+    "http://localhost"
+  }
+  return origin + at.mocode.frontend.core.domain.AppConstants.OIDC_REDIRECT_URI_JS_PATH
+}
+
+@OptIn(ExperimentalWasmJsInterop::class)
+private fun getWindowLocationOrigin(): String = js("window.location.origin")
+
+@OptIn(ExperimentalWasmJsInterop::class)
+private fun decodeURIComponent(encoded: String): String =
+  js("decodeURIComponent(encoded)")