Feature: Add "Clear input" button for input textarea (with confirmation)

## Title
Feature: Add "Clear input" button for input textarea (with confirmation)

## Description
Add a **Clear** button next to the existing **Paste** button to quickly reset the input textarea content. Implement this in **both the web app and the browser extension** for consistent UX.

## Acceptance Criteria
- [ ] Clicking **Clear** empties the textarea.
- [ ] Show a confirmation step (OK to use `confirm()`, a small modal, or a simple inline "Are you sure?") to prevent accidental clears.
- [ ] Must **not** break the existing word count behavior.
- [ ] Implemented in both web and extension for consistency.

## Files / Locations
- `eduaid_web/src/pages/Text_Input.jsx`
- `extension/src/pages/text_input/TextInput.jsx`

## Notes
Keep changes minimal. Avoid unrelated UI refactors or styling changes.