profile: allow users to toggle e-mail login notices

To avoid cluttering people's e-mail with tons of login notices, it seems like it would make sense to allow users to toggle if they want to hear them or not.

This adds a few checkboxes in `/profile/index` to allow people to toggle both failed login notices and successful login notices. They'll be checked by default.

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*Important*: If you merge this change, you'll receive errors if you don't modify the `user` table to include the new fields.
```sql
ALTER TABLE user ADD COLUMN login_success_notice BOOLEAN DEFAULT 1;
ALTER TABLE user ADD COLUMN login_failed_notice BOOLEAN DEFAULT 1;
```