[SakshiYeole]

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?

ciphers/base58.py was a byte-identical copy of ciphers/base64_cipher.py, so the repository had no Base58 implementation (see #15637). This replaces it with a Base58 encoder/decoder using the Bitcoin alphabet.

• base58_encode(data: bytes) -> bytes
• base58_decode(encoded_data: str | bytes) -> bytes
• Each leading zero byte is written as a leading 1 and restored on decode.
• Wrong input types raise TypeError; characters outside the alphabet (0, O, I, l, ...) raise ValueError.

The signatures mirror base64_cipher.py (bytes out, str or bytes accepted by the decoder), so the base* modules in ciphers/ stay consistent.

Note on the issue's examples: base58_encode(b"\x00\x01") is 12 (one leading zero byte gives one 1, and the value 1 is 2), and 2z decodes to b"s". The doctests use the verified values.

Verification: doctests pass; ruff check, ruff format and pre-commit pass; 12,600 random inputs (including leading zero bytes) match the PyPI base58 package in both directions. I also ran the full test suite locally (headless): the only 2 failures are web_programming/instagram_crawler.py (needs network) and machine_learning/linear_discriminant_analysis.py::gaussian_distribution, which fail identically on a clean upstream/master.

Fixes #15637

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".