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/composables/useSocial.ts

@@ -152,5 +152,5 @@ export function useSocial(relayUrls: string[]) {
 }
 
 // Export singleton instance for global use
-const relayUrls = JSON.parse(import.meta.env.VITE_NOSTR_RELAYS as string)
-export const social = useSocial(relayUrls)
+import { config } from '@/lib/config'
+export const social = useSocial(config.nostr.relays)