Fix minimum partition for negative numbers

[AbodiDawoud]

Describe your change:

Fix dynamic_programming/minimum_partition.find_min so it handles negative numbers consistently. The previous DP table used sums as indexes, so inputs like [-1] and [-1, -5, -10, -3] raised an internal IndexError even though the partition problem is still well-defined.

This now tracks reachable subset sums directly and returns the minimum absolute partition difference for both positive and negative integers.

• 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 #ISSUE-NUMBER".

Local checks:

• python3 -m doctest -v dynamic_programming/minimum_partition.py
• .venv/bin/python -m pytest dynamic_programming/minimum_partition.py
• .venv/bin/ruff check dynamic_programming/minimum_partition.py
• .venv/bin/ruff format --check dynamic_programming/minimum_partition.py
• .venv/bin/mypy --ignore-missing-imports dynamic_programming/minimum_partition.py
• git diff --check