feat: Add .env.example file and update Navbar for market navigation

- Introduce a new .env.example file for Nostr and API configuration, including settings for push notifications and market relays.
- Update Navbar.vue to include a new navigation item for the market, enhancing user access to market features.
- Extend localization support by adding market translations in English, Spanish, and French.

src/components/layout/Navbar.vue

@@ -28,6 +28,7 @@ const showProfileDialog = ref(false)
 const navigation = computed<NavigationItem[]>(() => [
   { name: t('nav.home'), href: '/' },
   { name: t('nav.events'), href: '/events' },
+  { name: t('nav.market'), href: '/market' },
 ])
 
 // Compute total wallet balance