refactor(auth, design-system): remove unused methods and annotations for cleanup

- Deleted obsolete methods such as `exchangeAuthorizationCode` and `logout` from the Auth module.
- Removed unused browser PKCE utilities and associated constants.
- Annotated unused components across the Design System with `@Suppress("unused")` for clarity.
- Simplified `LoginViewModel` to handle logout by clearing UI state directly.

frontend/core/auth/src/commonMain/kotlin/at/mocode/frontend/core/auth/data/AuthApiClient.kt

@@ -3,19 +3,11 @@ package at.mocode.frontend.core.auth.data
 import at.mocode.shared.core.AppConstants
 import io.ktor.client.*
 import io.ktor.client.call.*
+import io.ktor.client.request.*
 import io.ktor.client.request.forms.*
 import io.ktor.http.*
 import kotlinx.serialization.Serializable
 
-/**
- * Data classes for authentication API communication
- */
-@Serializable
-data class LoginRequest(
-  val username: String,
-  val password: String
-)
-
 @Serializable
 data class LoginResponse(
   val success: Boolean,
@@ -85,49 +77,6 @@ class AuthApiClient(
     }
   }
 
-  /**
-   * Exchange an authorization code (PKCE) for tokens
-   */
-  suspend fun exchangeAuthorizationCode(code: String, codeVerifier: String, redirectUri: String): LoginResponse {
-    val tokenEndpoint = "$keycloakBaseUrl/realms/$realm/protocol/openid-connect/token"
-    return try {
-      val response = httpClient.submitForm(
-        url = tokenEndpoint,
-        formParameters = Parameters.build {
-          append("grant_type", "authorization_code")
-          append("client_id", clientId)
-          if (!clientSecret.isNullOrBlank()) {
-            append("client_secret", clientSecret)
-          }
-          append("code", code)
-          append("code_verifier", codeVerifier)
-          append("redirect_uri", redirectUri)
-        }
-      ) {
-        contentType(ContentType.Application.FormUrlEncoded)
-      }
-
-      if (response.status.isSuccess()) {
-        val kc = response.body<KeycloakTokenResponse>()
-        LoginResponse(
-          success = true,
-          token = kc.access_token,
-          message = null
-        )
-      } else {
-        LoginResponse(
-          success = false,
-          message = "Code-Exchange fehlgeschlagen: HTTP ${'$'}{response.status.value}"
-        )
-      }
-    } catch (e: Exception) {
-      LoginResponse(
-        success = false,
-        message = "Code-Exchange Fehler: ${'$'}{e.message}"
-      )
-    }
-  }
-
   /**
    * Refresh authentication token
    */
@@ -169,15 +118,6 @@ class AuthApiClient(
     }
   }
 
-  /**
-   * Logout and invalidate token
-   */
-  suspend fun logout(token: String): Boolean {
-    // Empfehlung: Frontend-seitig Token lokal verwerfen.
-    // Optional könnten hier Keycloak-Endpoints für Token-Revocation aufgerufen werden.
-    return true
-  }
-
   @Serializable
   private data class KeycloakTokenResponse(
     val access_token: String,

frontend/core/auth/src/commonMain/kotlin/at/mocode/frontend/core/auth/data/AuthTokenManager.kt

@@ -70,6 +70,7 @@ data class AuthState(
  * to prevent XSS attacks. The token is lost when the browser tab is closed
  * or refreshed, requiring re-authentication.
  */
+@Suppress("unused")
 class AuthTokenManager {
 
   private var currentToken: String? = null

frontend/core/auth/src/commonMain/kotlin/at/mocode/frontend/core/auth/presentation/LoginViewModel.kt

@@ -46,6 +46,10 @@ class LoginViewModel(
         _uiState.value = _uiState.value.copy(
           isAuthenticated = authState.isAuthenticated
         )
+        // If logged out, clear credentials
+        if (!authState.isAuthenticated) {
+          _uiState.value = LoginUiState()
+        }
       }
     }
   }
@@ -129,15 +133,4 @@ class LoginViewModel(
       }
     }
   }
-
-  fun logout() {
-    authTokenManager.clearToken()
-    // Reset UI state (clear username/password)
-    _uiState.value = LoginUiState()
-  }
-
-  fun checkAuthenticationStatus() {
-    val isAuthenticated = authTokenManager.hasValidToken()
-    _uiState.value = _uiState.value.copy(isAuthenticated = isAuthenticated)
-  }
 }