Add internal authentication configuration and middleware support

- Enable internal authentication via environment variable in .env.example
- Update nuxt.config.ts to include internalAuthEnabled check
- Modify internal-auth middleware to conditionally enforce authentication based on the new configuration

nuxt.config.ts

@@ -51,6 +51,7 @@ export default defineNuxtConfig({
     databaseUrl: process.env.DATABASE_URL,
     redisHost: process.env.REDIS_HOST || 'localhost',
     redisPort: process.env.REDIS_PORT || '6379',
+    internalAuthEnabled: ['true', '1'].includes(process.env.INTERNAL_AUTH_ENABLED || '') || false,
     internalAuthUsername: process.env.INTERNAL_AUTH_USERNAME || '',
     internalAuthPassword: process.env.INTERNAL_AUTH_PASSWORD || '',
 
@@ -97,4 +98,4 @@ export default defineNuxtConfig({
       },
     },
   },
-})
+})