Add recursive factorial method with tests

[khushipy]

Describe your change:

• Added recursive implementations of Factorial in the recursion/ directory.
• Included proper type hints, doctests, and error handling.
• Added corresponding unit tests under recursion/tests/.
• Each function includes a reference URL (Wikipedia) in the docstring.

Adheres to all TheAlgorithms/Python contribution guidelines.

• 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 there is no recursion folder  #12142".

[khushipy]

My changes are limited to recursion/factorial.py. All related tests (recursion/tests/test_factorial.py) pass locally. The CI failures seem unrelated to this PR.