Remove all database dependencies and simplify application

BREAKING CHANGE: Remove all data analysis features

This commit removes all database-dependent functionality and simplifies
the application to focus on authentication and user management only.

Changes:
- Remove all /api/data and /api/metadata server endpoints
- Remove Supabase configuration from nuxt.config.ts and .env.example
- Remove @supabase/supabase-js dependency from package.json
- Delete data analysis pages: explorer, metadatos, rawExplorer, panorama,
  comparativa-cosechas, informe-ingresos
- Simplify sidebar navigation to show only "Inicio"
- Update home page to focus on authentication and profile management
- Remove "Supabase" and "Solo lectura" badges from navbar
- Keep only auth-related API endpoints: /api/auth/status and /api/auth/check-group

The application now serves as an authentication-protected portal with:
- Authentik SSO integration
- User profile management
- Settings and notifications pages (coming soon)
- No database or data analysis features

.env.example

@@ -1,6 +1,2 @@
-# Supabase Configuration
-SUPABASE_URL=https://your-project.supabase.co
-SUPABASE_SERVICE_ROLE_KEY=your-service-role-key
-
 # Authentik Configuration
 NUXT_PUBLIC_AUTHENTIK_URL=https://authentik.nucleoriofrio.com