fix: do not mutate caller-provided client_kwargs in LinkContentFetcher

[burakeyler]

Related Issues

Fixes #12828

Proposed Changes

LinkContentFetcher.__init__ stored the caller's client_kwargs dictionary and then called setdefault on it, so constructing the component added timeout and follow_redirects to a dictionary the application owns. Sharing one HTTP-client configuration between components leaked Haystack's defaults into the later use.

The dictionary is now shallow-copied before the defaults are applied.

How did you test it?

Added test_init_does_not_mutate_client_kwargs, which fails on main and passes here, and checked that the component still receives both defaults. pytest test/components/fetchers/test_link_content_fetcher.py -m "not integration" → 27 passed.

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title
• I documented my code
• I ran pre-commit hooks and fixed any issue

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[github-actions]

Hi @burakeyler, thanks for your interest in contributing to Haystack! 🙏

⚠️ Issue #12828 is already being addressed by open pull request(s) #12829. Before opening a PR for an issue, please check whether a PR is already linked to it, and consider contributing to the existing PR instead. We may close duplicate PRs to keep the review queue manageable.

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[github-actions]

Hi @burakeyler, thanks for your interest in contributing to Haystack! 🙏

⛔ First-time contributors can have at most 1 open pull request in this repository until it has been approved, so this PR was closed automatically. Your open pull request #12879 is unaffected. Once it has been approved by a maintainer, you are welcome to open more PRs. Feel free to reopen this one at that point.

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