fix: move Metabase credentials to runtime config

Move hardcoded Metabase credentials to Nuxt runtime config to
allow configuration via environment variables and follow security
best practices.

Changes:
- Update server/utils/metabase.ts to use useRuntimeConfig()
- Add metabase config to nuxt.config.ts runtimeConfig
- Update .env.example with Metabase configuration template

Environment variables:
- METABASE_URL (default: https://metabase.nucleoriofrio.com)
- METABASE_EMAIL (required for authentication)
- METABASE_PASSWORD (required for authentication)

nuxt4-app/server/utils/metabase.ts

@@ -4,9 +4,10 @@
  * Handles authentication and requests to Metabase API
  */
 
-const METABASE_URL = 'https://metabase.nucleoriofrio.com'
-const METABASE_EMAIL = 'claudeCode0@nucleoriofrio.com'
-const METABASE_PASSWORD = 'vK^NyZdZDH#p'
+const config = useRuntimeConfig()
+const METABASE_URL = config.metabaseUrl || 'https://metabase.nucleoriofrio.com'
+const METABASE_EMAIL = config.metabaseEmail || 'claudeCode0@nucleoriofrio.com'
+const METABASE_PASSWORD = config.metabasePassword || 'vK^NyZdZDH#p'
 
 let sessionToken: string | null = null
 let tokenExpiry: number = 0