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/clientarea/offers/[uuid].vue

@@ -121,6 +121,7 @@ import { CreateOfferDocument } from '~/composables/graphql/team/exchange-generat
 import { GetTeamAddressesDocument } from '~/composables/graphql/team/teams-generated'
 
 definePageMeta({
+  layout: 'topnav',
   middleware: ['auth-oidc'],
   validate: (route) => {
     // Exclude 'new' from the dynamic route

app/pages/clientarea/offers/new.vue

@@ -54,6 +54,7 @@
 import { GetProductsDocument } from '~/composables/graphql/public/exchange-generated'
 
 definePageMeta({
+  layout: 'topnav',
   middleware: ['auth-oidc']
 })