Docs: clarify supported Python versions and fix Windows dependency setup

[pranav-n29]

Title
Fix Windows backend installation issues by updating dependency constraints and clarifying supported Python versions

📝 Description
This PR fixes backend setup failures on Windows caused by incompatible dependency versions and unclear Python support.

🔧 What was change
Updated backend dependency constraints in requirements.txt to avoid versions that are not available on Windows.
Clarified backend Python support in README.md:
Explicitly document supported Python versions (3.9 – 3.11, recommended 3.10).
Clearly mention that Python 3.12+ and 3.13 are not supported due to native dependency issues (sentencepiece, spacy, pke, etc.)
Aligned installation instructions to reduce common setup errors for new contributors on Windows.

🐛 Problem fixed
Backend installation fails on Windows when running:
pip install -r requirements.txt
because some pinned versions (for example SciPy / PyTorch / native dependencies) are not available for certain Python versions
This PR improves the contributor experience by making the supported environment explicit and preventing incompatible installations.

🧪 Tested on
Windows 10
Python 3.10
Fresh virtual environment

🔗 Related issue
Closes / relates to:
#382 – BUG: Backend dependency installation fails on Windows

Summary by CodeRabbit

• Documentation
  • Updated backend requirements with supported Python versions (3.9–3.11, recommended 3.10)
  • Added Windows-specific dependency guidance
  • Clarified lack of support for Python 3.12+/3.13

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

📝 Walkthrough

Walkthrough

Documentation update replacing outdated permission-setting guidance with Python version compatibility requirements. Adds backend requirements section specifying supported Python versions (3.9–3.11) with 3.10 recommended and notes incompatibility with Python 3.12+/3.13.

Changes

Cohort / File(s)	Summary
Documentation Update README.md	Replaced troubleshooting note about execute permissions with "Backend requirements" section documenting supported Python versions (3.9–3.11, recommended 3.10) and noting lack of support for Python 3.12+/3.13 with Windows-specific caveats.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Poem

🐰 A changelog so spry, with versions made clear,
No more chmod mysteries, just Python to steer!
From 3.9 up to 3.11 we hop,
While 3.12 and beyond? We must stop!
Documentation's polished, requirements now bright. ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main changes: clarifying Python version support and fixing Windows dependency setup issues, which are the core objectives of this PR.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[SxBxcoder]

Hi! Thanks for checking the Python versions.

I’ve been working on the Windows backend fix too (PR #387), and I wanted to flag a conflict:

Security: The current pinned versions have critical RCE vulnerabilities (CVE-2025-3730). My PR #387 has already resolved the complex dependency chains needed to patch this without breaking scipy or numpy on Windows.

Documentation: This PR seems to remove the Set-ExecutionPolicy guide. I just pushed a fix for that in PR #390 because that command is actually required for many Windows users (including me) to get the venv running.

Since #387 already handles the security upgrades and dependency crashes, maybe we should review these together?