Add graph generation algorithm for Knapsack problems

[Matti02co]

Description:

This pull request adds a function to generate a directed acyclic graph (DAG) representation of a classic 0/1 Knapsack problem.
The graph representation enables solving the problem using shortest/longest path algorithms in DAGs, providing an alternative approach to traditional dynamic programming solutions.
Each path from the source node s to the sink node t corresponds to a valid subset of items.

Key points:

Input:

• capacity — maximum knapsack capacity (integer)

• weights — list of item weights (list of integers)

• values — list of item values (list of integers)

Output:

• List of edges, each represented as a dictionary containing "from", "to", "cost", and "label".

Implements Python type hints and doctests.

Code style follows PEP 8 and is Black-formatted.

Passes Ruff tests.

• 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".