Add authentication infrastructure for AGS

[victordibia]

Currently AGS lacks authentication, limiting its use in multi-user environments. We need to add authentication while maintaining ease of use.

Requirements

1. Add auth for API routes and WebSocket connections
2. Default mode: Works without configuration using local authentication (username/password)
3. Support for configurable OAuth providers (GitHub, Microsoft, etc.)
4. Update UI to load and apply auth config profiles etc.
5. Optional RBAC support?

Potential Approach (subject to change)

• FastAPI security dependencies for route protection
• Local auth with configurable admin credentials
• OAuth provider configuration via auth_config.yaml:

auth:
  enabled: true
  providers:
    local:
      enabled: true
      admin_user: admin
      admin_pass: changeme
    github:
      enabled: false
      client_id: ""
      client_secret: ""
...