feat!: secure-by-default symlink handling for ByteStream and converters

[ritikraj2425]

Related Issues

• fixes [Proposal] Security Hardening: Add symlink protection to ByteStream and Converters #11252

Proposed Changes:

Currently, ByteStream.from_file_path and the get_bytestream_from_source utility follow symbolic links by default when reading files from disk. This "blind follow" behavior could lead to accidental Local File Inclusion (LFI) or Information Disclosure if a developer passes a user-supplied path that happens to be a symlink to a sensitive system file.

This PR implements a "Secure by Default" approach:

• Added a follow_symlinks: bool = False parameter to ByteStream.from_file_path.
• If follow_symlinks is False (the new default), the method checks filepath.is_symlink() and raises a ValueError if a link is detected.
• Propagated this setting to the get_bytestream_from_source utility so that components reading file paths (like routers or converters) inherit this secure behavior.

How did you test it?

• Added unit tests in test/dataclasses/test_byte_stream.py to verify that ValueError is raised when trying to read a symlink with default parameters, and that it successfully reads it when follow_symlinks=True is explicitly passed.
• Added corresponding unit tests in test/components/converters/test_utils.py for get_bytestream_from_source.
• Verified changes locally using hatch run test:unit and hatch run test:types.

Notes for the reviewer

• The change uses .is_symlink() rather than aggressively resolving all parent paths to avoid breaking legitimate environments (like macOS /tmp directories which are often symlinked to /private/tmp).
• This change is isolated to the core dataclasses and utilities to keep the scope focused and avoid breaking the API of all individual converter components at once.

Checklist

• I have read the contributors guidelines and the code of conduct.
• I have updated the related issue with new insights and changes.
• I have added unit tests and updated the docstrings.
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test: and added ! in case the PR includes breaking changes.
• I have documented my code.
• I have added a release note file, following the contributors guidelines.
• I have run pre-commit hooks and fixed any issue.

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[anakin87]

See #11252 (comment)