Add YAML config and profile-based creation

Introduce a viper-backed YAML configuration system and profile-driven
instance creation to simplify deployment and reuse. This centralizes
flags into a single options definition and enables:

- persistent config files with command-line precedence and a generated
  packaging/config.yaml for packaging
- create-config.yaml profiles and file-include support for cloud-init and
  other external snippets, allowing multi-profile merging and overrides
- banner and welcome templates, built-in SFTP chroot option, and
  packaging changes to ship examples and defaults
- unified option handling via server/options.yaml and a generate step to
  produce the config template; allow dumping parsed configs for debugging

Also improve login string parsing and on-demand instance flow, add
supporting helpers (cron, tooling), and update various types/flags to
match the new config model.

Use first GitHub token from .netrc

Refactored incus shell, fixed host user group verification

Refactor instance user lookup to remove redundant checks.

add ignores

Connect to server before instance actions in ProxyDevice.