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/lib/config/index.ts

@@ -0,0 +1,69 @@
+// Centralized configuration management
+// Handles all environment variables and app configuration
+
+interface NostrConfig {
+  relays: string[]
+  adminPubkeys: string[]
+}
+
+interface ApiConfig {
+  baseUrl: string
+  key: string
+}
+
+interface AppConfig {
+  nostr: NostrConfig
+  api: ApiConfig
+  support: {
+    npub: string
+  }
+}
+
+// Parse JSON environment variables safely
+function parseJsonEnv(envVar: string | undefined, fallback: any = []): any {
+  if (!envVar) return fallback
+  
+  try {
+    return JSON.parse(envVar)
+  } catch (error) {
+    console.warn(`Failed to parse environment variable: ${envVar}`)
+    return fallback
+  }
+}
+
+// Create the configuration object
+export const config: AppConfig = {
+  nostr: {
+    relays: parseJsonEnv(import.meta.env.VITE_NOSTR_RELAYS, []),
+    adminPubkeys: parseJsonEnv(import.meta.env.VITE_ADMIN_PUBKEYS, [])
+  },
+  api: {
+    baseUrl: import.meta.env.VITE_API_BASE_URL || '',
+    key: import.meta.env.VITE_API_KEY || ''
+  },
+  support: {
+    npub: import.meta.env.VITE_SUPPORT_NPUB || ''
+  }
+} as const
+
+// Utility functions for common config operations
+export const configUtils = {
+  isAdminPubkey: (pubkey: string): boolean => {
+    return config.nostr.adminPubkeys.includes(pubkey)
+  },
+  
+  hasNostrConfig: (): boolean => {
+    return config.nostr.relays.length > 0
+  },
+  
+  hasApiConfig: (): boolean => {
+    return Boolean(config.api.baseUrl && config.api.key)
+  },
+  
+  getDefaultRelays: (): string[] => {
+    return config.nostr.relays
+  }
+}
+
+// Export individual config sections for convenience
+export const { nostr: nostrConfig, api: apiConfig } = config