fix(app): replace Vuetify 2 legacy props with proper V3 API

Replace deprecated V2 props that were being silently ignored:
- v-layout → v-row, grid-list-md removed, xs → cols on v-col
- v-tooltip top → location="top", v-list dense → density="compact"
- v-app-bar app/scroll-off-screen → scroll-behavior="hide"
- append-outer-icon → append-icon, remove primary-title
- headline class → text-h6, remove wrap from v-row

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/layouts/default.vue

@@ -1,7 +1,7 @@
 <template>
   <v-app :key='locale + isAuthenticated'>
-    <v-navigation-drawer v-model='nav' temporary app>
-      <v-list dense>
+    <v-navigation-drawer v-model='nav' temporary>
+      <v-list density="compact">
         <v-list-item v-if='isAuthenticated && user' :title='user.name' :prepend-avatar='user.picture' />
         <v-list-item>
           <v-switch v-model='darkMode' color='primary' :label="t('app.darkMode')" hide-details class='ms-1' />
@@ -35,7 +35,7 @@ v-if='isAuthenticated' link :title="t('app.logout')" prepend-icon='mdi-logout'
                      @click='doLogout' />
       </v-list>
     </v-navigation-drawer>
-    <v-app-bar app scroll-off-screen>
+    <v-app-bar scroll-behavior="hide">
       <v-app-bar-nav-icon @click='nav = !nav' />
       <v-toolbar-title :title='title' />
       <v-spacer />