feat(dynamic_programming): add Needleman-Wunsch global sequence align…

[Clear20-22]

Describe your change

• 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?

Add the Needleman–Wunsch algorithm (dynamic_programming/needleman_wunsch.py) for optimal global sequence alignment in $O(m \cdot n)$ time. This complements the existing smith_waterman.py local sequence alignment algorithm.

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".

Fixes #14440

[Copilot]

🟢 Approval recommended

No unresolved review comments remain.

Pull request overview

Adds a Needleman–Wunsch global sequence-alignment algorithm.

Changes:

• Implements dynamic-programming scoring and traceback.
• Supports configurable scoring parameters.
• Adds documentation and doctests.

File summaries

File	Summary
dynamic_programming/needleman_wunsch.py	New global sequence-alignment implementation with documentation and doctests.

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 0
• Review effort level: Lite

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