Implement a keyword-based SMS filter that automatically blocks messages containing specified keywords.

Expected Behavior:

If an incoming SMS contains the defined filter keyword(s):

The sender’s number is blocked (optional).

The message is hidden and not shown to the user.

Use Case:
This feature helps users avoid spam, fraud, or unwanted promotional messages based on custom keywords.

Example:

Filter word: "loan"

Incoming SMS: "Get an instant loan today!"

Result: The sender is blocked, and the message is not displayed.