feat: support boolean (CV_Bool) images in imwrite - #29407
## Summary
`imwrite` failed on `CV_Bool` (boolean) images because no encoder handles that depth. This normalizes a boolean image to `CV_8U` (mapping true to 255) before encoding, so boolean masks can be written directly instead of requiring a manual `convertTo` at every call site.
Adds round-trip tests covering boolean-image encoding.
Fixes#29365
AI was used for assistance.
APNG encoding optimization #26849
related #26840
### Pull Request Readiness Checklist
See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request
- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
Patch to opencv_extra has the same branch name.
- [ ] The feature is well documented and sample code can be built with the project CMake
