Prevent Loading Without Input and Add Alert for Missing Data

# Description:

## Current Behavior:

The ***"Next"*** button initiates the loading process even when no input (text, file, or URL) is provided.

## Expected Behavior:

The ***"Next"*** button should validate the input fields and:
1. Display an alert if no input is provided.
2. Prevent the loading process from starting until valid input is given.

## Proposed Solution:

1. Add a validation check to ensure input is provided in one of the fields (text, file, or URL).
2. Display a concise alert: "Please provide input (text, file, or URL) to generate your quiz."
Stop execution and prevent loading if validation fails.

## Pros of the Fix:

1. Improves User Experience:

-Prevents confusion by guiding the user to provide necessary input.

2. Enhances Validation:

-Reduces unnecessary backend requests, optimizing system performance.

3. Error Prevention:

-Eliminates the risk of sending empty data to the backend.

4. Professional Workflow:

-Aligns the application behavior with expected user interaction patterns.

5. Efficiency:

-Saves user time by clearly communicating the issue upfront.