Sync notification when back online

### Steps to reproduce

1. go offline (f.e. over night, plane mode/wifi off)
2. get messages while offline
3. go back online, but not receiving messages
4. open app, messages and notifications appear

I guess there is some kind of event in android like _network changed_ or _network connection established_.
When going back online there should happen a sync.
WhatsApp and Signal does this too (visible through shortly appearing notifications)

### Outcome

#### What did you expect?
Messages and notifications get synced if network changed
#### What happened instead?
Notifications not shown

### Your phone model

_No response_

### Operating system version

Android 11

### Application version and app store

_No response_

### Homeserver

_No response_

### Will you send logs?

No

### Are you willing to provide a PR?

No