[FR]: Notification permission dialog should not be shown immediately on first run

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Describe the problem

After running the app for the first time, the notification permission dialog is shown immediately. This is not a great user experience because the user doesn't have enough context to know what notifications are going to be shown, or how frequently.

### Describe the solution

The notification permission dialog should only be shown after the user has completed the onboarding (i.e. chosen topics they are interested in) and there should be some additional information shown saying something like:

"Would you like to be informed when new content is published on these topics, content is typically published every few days? [Yes/No]"

If yes, show the notification permission dialog.

### Additional context

_No response_

### Code of Conduct

- [X] I agree to follow this project's Code of Conduct

No files or tests are named in the issue. Start by tracing where the first-run notification permission is requested and how onboarding records the selected topics; the work is done when the request occurs only after onboarding, with the described explanatory prompt shown before the system dialog when the user agrees.

Written by the indexing model from the issue text.