feat: Centralize configuration management for Nostr and API settings

- Introduce a new config module to manage Nostr relays, admin pubkeys, and API settings.
- Update components to utilize the centralized config instead of environment variables directly.
- Refactor relevant files to improve maintainability and reduce reliance on environment variables.

src/App.vue

@@ -8,8 +8,9 @@ import { Toaster } from 'vue-sonner'
 import { useNostr } from '@/composables/useNostr'
 import { identity } from '@/composables/useIdentity'
 import { toast } from 'vue-sonner'
+import { config } from '@/lib/config'
 
-const relays = JSON.parse(import.meta.env.VITE_NOSTR_RELAYS as string)
+const relays = config.nostr.relays
 const { isConnected, isConnecting, error, connect, disconnect } = useNostr({ relays })
 
 const showPasswordDialog = ref(false)