docs: add session log for Keycloak fixes and role-based dashboard POC

- Logged details of the session addressing compiler warnings and roles in the dashboard POC under `docs/99_Journal/2026-03-19_Session_Log_POC_Rollen_Keycloak.md`.
- Documented Keycloak realm import challenges and resolution strategy for PostgreSQL volume reset.
- Verified JWT role extraction and dashboard routing logic for ADMIN and ORGANIZER roles.
- Included session outcomes and next steps for further validation and testing of the POC setup.

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

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

@@ -75,8 +75,10 @@ data class AuthState(
 @Suppress("unused")
 class AuthTokenManager {
 
-  // Shared Json instance to avoid redundant creation
-  private val jsonParser = Json { ignoreUnknownKeys = true }
+  companion object {
+    // Shared Json instance – einmalig erstellt, nicht bei jedem Aufruf
+    private val jsonParser = Json { ignoreUnknownKeys = true }
+  }
 
   private var currentToken: String? = null
   private var tokenPayload: JwtPayload? = null