feat: automate PR classification by line changes using secure Size Labeler workflow

[DebasmitaBose0]

Closes #5324

Summary

Implements an automated, secure pull request size labeler workflow to classify and tag PRs based on total line modifications.

Changes Made

• Authored .github/workflows/pr-size-labeler.yml.
• Created an intelligent line calculation script that filters out lockfiles and mock datasets.
• Handled label cleanup routines to dynamically re-evaluate size on PR updates.

Testing

• Tested the bash git-diff commands locally on dynamic branches against master.
• Verified that all labeling methods adhere to standard GITHUB_TOKEN write access policies.

Impact

Improves review efficiency and developer experience by providing immediate scope visibility on all incoming contributions.

Checklist

• Code follows project standards
• Tested locally
• No unrelated changes included
• Responsive design verified
• Accessibility considered

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