docs: add Custom Python component documentation

[MonikaFeigler]

Jira issue(s): PROOF-XXX (to be created)

Changes:

• Add new documentation page for the Custom Python application at /components/applications/custom-python/
• Add navigation entry under Components → Applications

Content is sourced from the component-custom-python README and covers:

• Comparison to Python Transformations
• Configuration parameters (Python version, source, Git settings, user parameters)
• Code examples using CommonInterface (tables, files, state, error handling, logging)
• Git repository integration with dependency management (pyproject.toml/uv.lock vs requirements.txt)

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Notes for reviewer

• No screenshots included — other application pages (e.g., Data Gateway) have UI screenshots. Consider whether screenshots of the component's configuration UI should be added before merging.
• Code-heavy content — the page includes extensive CommonInterface code examples. Please assess whether this level of detail is appropriate for user-facing docs or if some should live on developers.keboola.com instead.
• Verify the example repo link is publicly accessible.
• No redirect_from in front matter — intentional since this is a new page with no legacy URL.

Release Notes

Justification, description

New user documentation for the Custom Python component (application), enabling users to find guidance on configuring and using the component directly from help.keboola.com.

Plans for Customer Communication

N/A

Impact Analysis

Documentation-only change. No functional impact.

Deployment Plan

Standard merge to main — auto-deployed via Jekyll build.

Rollback Plan

Revert the merge commit.

Post-Release Support Plan

N/A

Link to Devin session: https://app.devin.ai/sessions/e9ef647896ee46529d9e0eda29d2b962
Requested by: @MonikaFeigler

[devin-ai-integration]

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[MonikaFeigler]

Summary

• Add new documentation page for the Custom Python application at /components/applications/custom-python/
• Add navigation entry under Components → Applications
• Rewrote content to be user-facing rather than developer-facing: replaced 9 code examples with a single minimal snippet and a link to developer docs,
  removed raw JSON configuration examples, removed JSON parameter key names from UI field descriptions
• Added 5 UI screenshots covering the component overview, Python version selection, inline code editor, User Parameters, and Git repository configuration

[MonikaFeigler]

@kudj can you please review this docs for custom python please?

[jordanrburger]

It would be great to have a note on this page about the possibility of configuring the custom python component easily with Kai.

[MonikaFeigler]

@jordan.burger great comment. Feel free to propose changes and send it to me for review. Thank you. 🙂