Add input validation for year, round, and institute type selections in CLI

[sparshsinghal885]

What this PR does:

• Refactors the following functions to validate user input and prevent invalid selections:
  1. josaa_rounds_year()
  2. josaa_rounds()
  3. csab_rounds_year()
  4. csab_rounds()
  5. csab_institute_types()
  6. josaa_institute_types()

Improvements:

• Uses while-loops instead of recursion to handle invalid input.
• Prints clear error messages when the user enters invalid options.
• Ensures variables are always assigned before proceeding.
• Prevents runtime errors such as UnboundLocalError.
• Makes the CLI more user-friendly and robust.

How to Test:

1. Run the CLI tool.
2. Enter invalid inputs for year, round, and institute type selections.
3. Confirm that the tool keeps prompting until a valid option is entered.
4. Confirm that valid selections proceed as expected.

[ksauraj]

LGTM, thanks @sparshsinghal885