- Updated the default `instance.theme` to `blue`, making it the new out-of-the-box look. The previous default `navy` can still be used by explicitly setting `AGNES_INSTANCE_THEME`.
- Pre-login pages now respect the configured `instance.theme`, eliminating the abrupt color change after sign-in for navy-configured instances.
- Adjusted documentation and code comments to reflect the new theme settings and their implications for existing instances.
- Version bump to 0.55.6 to reflect these changes.