feat: add Discover page — cypherpunk app store with sovereignty messaging

- New Discover.vue with hero banner, featured sovereignty stack apps,
  principle cards, manifesto footer, and full app grid
- Featured apps (Bitcoin Knots, LND, BTCPay, Vaultwarden) with
  expanded privacy/sovereignty descriptions
- Discover is first tab in categories bar on App Store pages
- Smart back navigation: detail pages return to Discover when navigated from there
- Category clicks from Discover navigate to Marketplace with category pre-selected
- Cypherpunk aesthetic: terminal tags, scanline overlays, gradient accents,
  animated Bitcoin orange headings
- Global CSS classes: discover-hero, discover-terminal-tag, discover-featured-card,
  discover-principle-card, discover-manifesto
- Route added: /dashboard/discover

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

neode-ui/src/views/AppDetails.vue

@@ -644,12 +644,12 @@ useModalKeyboard(
 
 // Determine back button text based on where user came from
 const backButtonText = computed(() => {
-  // Check if we came from marketplace via query parameter
+  if (route.query.from === 'discover') {
+    return 'Back to Discover'
+  }
   if (route.query.from === 'marketplace') {
     return t('appDetails.backToStore')
   }
-
-  // Default to My Apps
   return t('appDetails.backToApps')
 })