feat(navigation): activities fragment

[alperozturk96]

Changes

Converts ActivitiesActivity to fragment
Adds a navigation stack to Navigator
Adds action bar style
Configures action bar styles between pushes and pop thus no more duplicated logic we will have and no more mismatch

[github-actions]

APK file: https://github.com/nextcloud/android/actions/runs/23589054007/artifacts/6120749964
To test this change/fix you can simply download above APK file and install and test it in parallel to your existing Nextcloud app.
(please click on link to get QR code displayed)

[github-actions]

blue-Light-Screenshot test failed, but no output was generated. Maybe a preliminary stage failed.

[github-actions]

Codacy

SpotBugs

Category	Base	New
Bad practice	39	39
Correctness	74	70
Dodgy code	236	236
Experimental	1	1
Internationalization	7	7
Malicious code vulnerability	2	2
Multithreaded correctness	34	34
Performance	43	42
Security	18	17
Total	454	448

[github-actions]

APK file: https://github.com/nextcloud/android/actions/runs/23589595985/artifacts/6121109205
To test this change/fix you can simply download above APK file and install and test it in parallel to your existing Nextcloud app.
(please click on link to get QR code displayed)