Refactored the `AnnotationCreateDto` class:
- Changed `ElementId` from `int` to `long` and made it mutable.
- Marked `Name`, `Value`, and `Type` as `[Obsolete]` with defaults.
- Added `[Obsolete]` attributes to `Width` and `Height`.
- Introduced a new `Page` property to replace `SignatureDto`.
Updated `appsettings.json`:
- Set `Api.BaseUrl` to an empty string.
- Introduced AnnotationCreateDto for creation-specific properties
- AnnotationDto now inherits from AnnotationCreateDto and includes Id, AddedWhen, ChangedWhen, and ChangedWho
- Added Type property to AnnotationCreateDto
- remove CreateAnnotationCommand
