[BUG]: Fix input validation and prevent unnecessary API calls in Text_Input.jsx

### Bug Description

### Problem

The Text_Input component allows API calls even when the input is invalid or incomplete:

- Clicking "Next" without entering text or URL still triggers processing
- Invalid or empty Google Doc URLs may lead to unintended API calls
- Number of questions can be set to 0, which should not be allowed
- Error handling is inconsistent for file uploads and API failures
- Unused state variables add unnecessary clutter to the component

### Expected Behavior

- API calls should only be made when valid input is provided
- Either text input, file upload, or a valid Google Doc URL must be present
- Number of questions must be greater than 0
- Errors should be clearly displayed to the user
- Code should not contain unused state or redundant logic

### Proposed Solution

- Add validation to prevent empty input submission
- Prevent API calls when question count is 0
- Improve handling of Google Doc URL responses
- Handle file upload errors more safely
- Remove unused state variables to clean up the code

### Steps to Reproduce

_No response_

### Logs and Screenshots

_No response_

### Environment Details

_No response_

### Impact

Critical - Application is unusable

### Code of Conduct

- [x] I have joined the [Discord server](https://discord.gg/hjUhu33uAn) and will post updates there
- [x] I have searched existing issues to avoid duplicates