FireWatch: Notification emails

**Describe the task**
Add a feature to send notification emails to an email distribution list.

subscribe and remove an email notification emails for a distribution list.

**Acceptance Criteria**
- [ ] There is an option to subscribe one or more emails to notifications.
- [ ] There is an option to remove an email from notifications.
- [ ] There is an option to notify only when burning conditions are met in the forecast or notify all the time.
- [ ] The email notification includes a link back to the FireWatch and the specified entry.

**Additional context**
- Add any other context about the task here.
- Or here

No files, tests, or entry points are named. Start by locating the FireWatch notification and forecast-related components, then trace how distribution-list subscriptions and entry links are represented; done means subscribe, remove, conditionally notify, and link back to the specified entry all work.

Written by the indexing model from the issue text.