fix(maths): defer Matrix type annotations so import does not NameError

[sudo-ai-git]

Describe your change:

Fix a bug in matrix_exponentiation: importing the module raised NameError: name 'Matrix' is not defined because the class method annotations reference Matrix before it is defined (eager annotation evaluation). Add from __future__ import annotations to defer annotation evaluation.

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Add or change doctests? -- Note: Please avoid changing both code and tests in a single pull request.
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python [type hints].
• All functions have [doctests] that pass the automated testing.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
• If this pull request resolves one or more open issues then the description above includes the issue number(s) with a [closing keyword]: "Fixes [BUG] NameError on self-referential class type annotations in matrix_exponentiation.py #15075".

Fixes #15075. Verified: import now succeeds, fibonacci_with_matrix_exponentiation(13,0,1) == 144, doctests pass. Minimal change (add one __future__ import line only).