feat(portal): redesign registration wizard, header and login with Vuexy patterns

- Registration page: switch to blank layout with split-screen design (event branding
  illustration on left, AppStepper wizard on right), replacing generic chip stepper
- Portal header: refined to flat surface bar with proper branding and icon-based nav
- Login page: upgrade to Vuexy V2 auth pattern with split-screen illustration
- Success page: blank layout with centered card, avatar icon, and footer mask

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/portal/src/layouts/portal.vue

@@ -36,55 +36,90 @@ watch([isFallbackStateActive, refLoadingIndicator], () => {
     <AppLoadingIndicator ref="refLoadingIndicator" />
 
     <VAppBar
-      color="primary"
+      flat
+      color="surface"
+      border="b"
       density="comfortable"
     >
-      <VAppBarNavIcon
-        class="d-sm-none"
-        @click="isMobileMenuOpen = !isMobileMenuOpen"
-      />
+      <VContainer
+        fluid
+        class="d-flex align-center py-0"
+        style="max-inline-size: 1440px;"
+      >
+        <!-- Logo & Brand -->
+        <RouterLink
+          to="/"
+          class="d-flex align-center gap-x-2 text-decoration-none"
+        >
+          <VIcon
+            icon="tabler-users-group"
+            size="26"
+            color="primary"
+          />
+          <span class="text-h6 font-weight-bold text-high-emphasis">
+            Crewli
+          </span>
+        </RouterLink>
 
-      <VAppBarTitle class="text-h6">
-        Crewli Portal
-      </VAppBarTitle>
+        <!-- Mobile nav toggle -->
+        <VAppBarNavIcon
+          class="d-sm-none ms-auto"
+          @click="isMobileMenuOpen = !isMobileMenuOpen"
+        />
 
-      <template #append>
-        <div class="d-none d-sm-flex align-center gap-2">
+        <!-- Desktop navigation -->
+        <div class="d-none d-sm-flex align-center gap-1 ms-6">
           <VBtn
             v-for="item in navItems"
             :key="item.to"
             :to="item.to"
             variant="text"
-            color="white"
+            color="default"
+            size="small"
+            class="text-medium-emphasis"
           >
             <VIcon
               start
               :icon="item.icon"
+              size="18"
             />
             {{ item.title }}
           </VBtn>
         </div>
 
+        <VSpacer />
+
+        <!-- Auth actions -->
         <VBtn
           v-if="authStore.isAuthenticated"
-          variant="outlined"
-          color="white"
-          class="ms-2"
+          variant="tonal"
+          color="primary"
+          size="small"
           @click="authStore.logout(); $router.push('/login')"
         >
+          <VIcon
+            start
+            icon="tabler-logout"
+            size="18"
+          />
           Uitloggen
         </VBtn>
 
         <VBtn
           v-else
-          variant="outlined"
-          color="white"
-          class="ms-2"
+          variant="tonal"
+          color="primary"
+          size="small"
           to="/login"
         >
+          <VIcon
+            start
+            icon="tabler-login"
+            size="18"
+          />
           Inloggen
         </VBtn>
-      </template>
+      </VContainer>
     </VAppBar>
 
     <!-- Mobile navigation drawer -->
@@ -126,6 +161,7 @@ watch([isFallbackStateActive, refLoadingIndicator], () => {
       <VContainer
         fluid
         class="pa-4 pa-sm-6"
+        style="max-inline-size: 1440px;"
       >
         <RouterView v-slot="{ Component }">
           <Suspense