feat: add prompt versioning feature

[AkshayasriM]

Description

This PR introduces the initial implementation of the Prompt Versioning feature.

Changes Made

• Added automatic prompt version saving using localStorage.
• Added a Version History button in the editor.
• Added a Version History panel to display saved prompt versions.
• Created prompt-versioning.js to manage prompt version storage and retrieval.
• Integrated the feature without affecting the existing AI generation workflow.

Related Issue

Fixes #1631

Type of change

• Bug fix
• New feature / enhancement
• Documentation update
• Test addition
• Refactor

Checklist

• I have read CONTRIBUTING.md
• My branch is up to date with main
• I have run pytest -v and all tests pass
• I have not introduced duplicate issues or features
• My PR title follows the format: feat/fix/docs/test: short description
• I have added tests for new features (Level 2 and 3 issues)
• No hardcoded secrets or API keys in my code
• This PR is linked to a GSSoC 2026 issue

Screenshots (if frontend change)

Before

(Add a screenshot of the editor before the Version History feature.)

After

(Add a screenshot showing the Version History button/panel after your changes.)

[imDarshanGK]

@AkshayasriM Please attach a short demo video showcasing the implemented feature.