refactor(ui, navigation): implement platform-specific routing and redesign components

- Added platform detection logic `currentPlatform()` in `PlatformType.js.kt`.
- Introduced platform-based behavior for LandingScreen, Dashboard, and Login flow.
- Replaced Row with FlowRow in PingScreen to improve button layout.
- Updated Meldestelle Dashboard with platform-specific headers and authentication checks.
- Adjusted AppHeader to accept `isAuthenticated` and `username` parameters.

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

config/docker/keycloak/meldestelle-realm.json

@@ -61,6 +61,12 @@
         "composite": false,
         "clientRole": false
       },
+      {
+        "name": "ORGANIZER",
+        "description": "Veranstalter role for managing tournaments",
+        "composite": false,
+        "clientRole": false
+      },
       {
         "name": "MONITORING",
         "description": "Monitoring role for system health checks",
@@ -301,6 +307,26 @@
           "ADMIN"
         ]
       }
+    },
+    {
+      "username": "urfv_neumarkt",
+      "enabled": true,
+      "emailVerified": true,
+      "firstName": "URFV",
+      "lastName": "Neumarkt",
+      "email": "office@urfv-neumarkt.at",
+      "credentials": [
+        {
+          "type": "password",
+          "value": "Turnier#2026",
+          "temporary": false
+        }
+      ],
+      "realmRoles": [
+        "USER",
+        "ORGANIZER"
+      ],
+      "clientRoles": {}
     }
   ],
   "groups": [],