[FEATURE] Add CLI Support for Encryption/Decryption Operations

[snehaapratap]

Please describe.
I'm always frustrated when I need to manually input text or rely on GUI elements for encryption/decryption processes, especially when working in terminal environments, creating scripts, or automating tasks. The current tool lacks a command-line interface (CLI), limiting its use in non-GUI environments and automated pipelines.

Proposed Solution

• Implement a Python-based CLI using the argparse module that allows users to:
• Choose encryption method (rsa or caesar)
• Select mode (encrypt or decrypt)
• Input text directly via command line or from a file
• (For RSA) Automatically generate keys or input custom keys
• (For Caesar) Input shift key
• View output in the terminal or save results to a file

Additional context

• Adds accessibility for users working in headless servers or automation environments.

• Encourages modular design and easier testing of individual components.

• Great starting point for contributors wanting to learn argparse, text processing, and crypto basics in Python.

• Can later be extended with features like batch processing or API endpoints.