Major upgrade to the CLI version of the Internet Speed Test App

[atharvabaodhankar]

Summary

This PR brings a major upgrade to the CLI version of the Internet Speed Test App:

• Modern, user-friendly CLI UI using the rich library (colored panels, tables, spinners)
• Displays local and external IP, ISP, and location before the test
• Shows server info and test time in the results table
• Friendly error handling: if the test fails, the user can retry
• Option to save results to a file (speedtest_results.txt) after a successful test
• Code cleanup: constants for clarity, improved structure
• README updated to reflect all new features and usage

Motivation

These changes make the CLI much more pleasant and robust for users, and provide a more professional, informative, and interactive experience.

How to Test

• Run python speed_test_cli.py
• Try with/without internet, and test retry and save features
• Check the output and saved file

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