[BUG]: Extension fails because manifest host_permissions use :8000 while fetch calls use :5000

### Bug Description

## Summary

The Chrome extension is configured with a backend host permission for `http://127.0.0.1:8000/*`, but the extension code actually sends requests to `http://localhost:5000/*`.

Because of that mismatch, extension requests to the local EduAid backend can fail silently or be blocked.

## Evidence

Manifest:
- `extension/public/manifest.json`
- current host permission: `http://127.0.0.1:8000/*`

Extension fetch calls:
- `extension/public/youtubeContentScript.js`
- `extension/src/pages/text_input/TextInput.jsx`
- `extension/src/pages/answer/Answer.jsx`
- `extension/src/pages/question/Question.jsx`
- `extension/src/pages/question/SidePanel.jsx`

These all target `http://localhost:5000/...`

## Expected

The extension should have host permissions that match the backend URLs it actually calls.

## Actual

The manifest allows `127.0.0.1:8000`, while the code calls `localhost:5000`.

## Proposed fix

Update `extension/public/manifest.json` to allow:
- `http://localhost:5000/*`
- `http://127.0.0.1:5000/*`

This is a small manifest-only fix and does not require backend changes.

### 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