[P2] Remove Fragments, XML layouts, ViewBinding and nav XML

[amaury901130]

Delete BaseFragment, BaseNavActivity, OnBoardingActivity, LoadingDialogUtil, layouts and navigation XML once Compose screens are in.

Acceptance criteria

• No Fragment or layout XML left
• viewBinding/dataBinding disabled

Reference: Android Base — Modernization Audit & Recommendations — section: Jetpack Compose migration