fix: register mangled image names to prevent export collisions

[Niruhqs]

Fixes #8076

Motivation and context

mangle_image_name() resolves filename collisions during project export by trying candidates like image_1, image_1_1, etc. When it finds a free candidate, it only increments the counter for the original name in the names tracking dict, never registering the candidate itself as taken.

If task order in the project causes the fallback names to be generated before the real files that happen to share those names are processed, the real files are later returned unchanged (since their name was never marked as taken) and silently overwrite the earlier export, exactly as described in the issue.

The fix registers every name actually handed out, not just the original name's counter, so a later real file with a colliding name gets re-mangled instead of overwriting an already-exported image.

How has this been tested?

Added test_export_project_with_duplicate_image_names_across_tasks to tests/python/rest_api/test_projects.py, modeled on the existing test_export_project_with_honeypots test: creates a project with two tasks whose images share the same original filename, exports it, and asserts both survive as distinct files with matching annotation entries.

Verified the fix in isolation with a standalone script reproducing the collision scenario from the issue (5 tasks with a duplicate image.jpg, followed by a task with the real image_1.jpg to image_4.jpg): the current code produces 4 collisions, the fix produces 0.

I was not able to run the full test suite locally (no local CVAT dev/Docker environment set up), so I'd appreciate CI/reviewer confirmation that the added test passes.

Checklist

I submit my changes into the develop branch. I have added a description of my changes into the CHANGELOG file (to follow up once this PR's number is known). I have updated the documentation accordingly (not applicable, internal helper function). I have added tests to cover my changes. Related issue is linked above via "Fixes #8076".

License

I submit my code changes under the same MIT License that covers the project.

[claude]

Claude Code Review

This pull request is from a fork — automated review is disabled. A repository maintainer can comment @claude review to run a one-time review.

[zhiltsov-max]

Consider doing this to test the issue being fixed:

Suggested change

	image_files = generate_image_files(1, filenames=["image.jpg"])
	task_params = {
	image_files = generate_image_files(
	3, filenames=["image.jpg", "image_1.jpg", "image_1_1.jpg"]
	)
	task_params = {

[zhiltsov-max]

Suggested change

	"name": task_name,
	"segment_size": 1,
	"project_id": project.id,
	}
	"name": task_name,
	"project_id": project.id,
	}

segment size is irrelevant here

[zhiltsov-max]

Suggested change

	assert len(set(exported_image_names)) == 2
	with zip_file.open("annotations/instances_default.json") as anno_file:
	annotations = json.load(anno_file)
	annotated_names = [a["file_name"] for a in annotations["images"]]
	assert len(set(annotated_names)) == 2
	assert sorted(annotated_names) == sorted(exported_image_names)
	assert len(exported_image_names) == 6
	assert len(set(exported_image_names)) == 6
	with zip_file.open("annotations/instances_default.json") as anno_file:
	annotations = json.load(anno_file)
	annotated_names = [a["file_name"] for a in annotations["images"]]
	assert len(set(annotated_names)) == 6
	assert sorted(annotated_names) == sorted(exported_image_names)

[zhiltsov-max]

Suggested change

	- Project export could silently overwrite images across tasks when
	filename collisions were resolved with a generated fallback name that
	was never marked as taken
	(<https://github.com/cvat-ai/cvat/pull/10915>)
	- Project export could silently overwrite images across tasks after resolving filename collisions
	(<https://github.com/cvat-ai/cvat/pull/10915>)

[zhiltsov-max]

Hi, thank you for sending the PR. Please address the comments.