Pin movement to >0.17.0 and rename dims to singular

[niksirbi]

Description

What is this PR

• Bug fix
• Addition of a new feature
• Other

Why is this PR needed?

movement v0.1.70 introduced an important breaking change.

The xarray dimension names "keypoints" and "individuals" have been renamed to "keypoint" and "individual", following standard pandas/xarray conventions where dimensions represent variable names, not collections.

What does this PR do?

• Pins the movement dependency in pyproject.toml to >=0.17.0
• Renames all occurrences of the dimensions names individuals and keypoints to the singular forms individual and keypoint

Merging this PR may cause some workflows to break, but in most cases a simple dimension rename will fix them.

References

Needed to unblock #57 and #56

How has this PR been tested?

Existing tests pass locally.

Is this a breaking change?

Yes!

Does this PR require an update to the documentation?

No, but I've checked that docs build succesfully locally.

Checklist:

• The code has been tested locally
• Tests have been added to cover all new functionality
• The documentation has been updated to reflect any changes
• The code has been formatted with pre-commit