Remove default layout, migrate all pages to topnav

- Add layout: 'topnav' to all 27 pages that were using default layout
- Delete app/layouts/default.vue

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/pages/search/index.vue

@@ -29,7 +29,10 @@
   </Stack>
 </template>
 
-<script setup>
+<script setup lang="ts">
+definePageMeta({
+  layout: 'topnav'
+})
 
 const localePath = useLocalePath()
 const { t } = useI18n()