feat: add confirmation dialog before clearing history and favorites

[jess2937]

Description

This PR adds a safety confirmation dialog to preventing accidental data loss when a user clicks the "Clear" buttons. Specifically, it introduces a window.confirm() popup when a user attempts to clear either their history or their saved favorites. If the user clicks "Cancel", the deletion process is safely aborted.

Related Issue

Fixes #167

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)

Confirmation Dialog View:

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Test evidence

# Frontend changes verified manually in browser environment.
# Local execution of pytest encountered dependency resolution issues (ModuleNotFoundError for backend frameworks), which is unrelated to the frontend HTML confirmation UI implementation. 
# Action verified manually: Click event triggers browser confirmation box; 'Cancel' successfully returns/aborts deletion sequence; 'OK' execution clears application state items as expected.
<img width="1138" height="323" alt="image" src="https://github.com/user-attachments/assets/048701ac-e218-4d55-a73f-160fc8b30284" />

[jess2937]

Hi @imDarshanGK ! 👋

I have completed the implementation for this feature.

Summary of changes:

• Explicitly bound the confirmation logic to the global scope by updating the calls to window.confirm() within the clearHistoryBtn and clearFavsBtn click handlers inside frontend/index.html.
• This ensures maximum reliability, aligns with web development best practices, and prevents any potential scope-resolution bugs in the frontend.

The PR template has been filled out. Ready for your review and feedback whenever you have time! Thank you.