Notification policy (#4768)

This was so much work wow. I think it works pretty well and is the best
compromise between all the alternative we considered. Yes the
pull-to-refreh on the notifications works slightly different now when
the new bar is visible, but I don't think there is a way around that.

Things I plan to do later, i.e. not as part of this PR or release:
- Cache the notification policy summary for better offline behavior and
less view shifting when it loads
- try to reduce some of the code duplications that are now in there
- if there is user demand, add a "legacy mode" setting where this
feature is disabled even if the server would support it

closes #4331
closes #4550 as won't do
closes #4712 as won't do

<img
src="https://github.com/user-attachments/assets/de322d3c-3775-41e7-be57-28ab7fbaecdf"
width="240"/> <img
src="https://github.com/user-attachments/assets/1ce958a4-4f15-484c-a337-5ad93f36046c"
width="240"/> <img
src="https://github.com/user-attachments/assets/98b0482b-1c05-4c99-a371-f7f4d8a69abd"
width="240"/>

app/src/main/res/drawable/badge_background.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android"
+    android:shape="rectangle">
+    <corners android:radius="6dp" />
+    <solid android:color="?attr/colorPrimary" />
+</shape>