Push notification filter from people I follow isn't working

I have push notifications enabled for people I follow, but I get notifications from everyone, including people I don't follow.

- Which site: phanpy.social
- Which site version: 2024.03.17.c7c764a
- Which instance: carfree.city, running v4.0.15+hometown-1.1.1

**To Reproduce**
Steps to reproduce the behavior:
1. Install Phanpy to home screen via iPhone Safari
2. Go to Settings, Push Notifications (Beta)
3. Select Mentions
4. Select "People I follow"
5. Wait for someone I don't follow to reply/mention me

**Expected behavior**
Mentions should notify me for people I follow, but not for people I don't follow.

**Screenshots**

My settings:


**Smartphone**
- Device: iPhone X
- OS: 17.3.1
- Browser: Safari via add to home screen

**Additional context**
I also experience bug #317, where the notification settings appear to be reset each time I open the settings panel. However, other settings changes seem to persist, such as having notifications on, and limited to certain notification types (i.e., not boosts and likes).

Start in Settings > Push Notifications (Beta) and reproduce the issue on an iPhone using Safari's home-screen installation, selecting Mentions and People I follow. Trace how the selected audience is stored and applied to incoming mention notifications; done means mentions from followed people notify while mentions from other people do not, without breaking the other notification filters.

Written by the indexing model from the issue text.