feat: add TopAppBar with back arrow and proper navigation back stack

feat: production MVVM frontend with 5 screens, navigation, and theme

feat: initialize native Android frontend app structure

merge: restructure project into backend/frontend layout with modularized services

docs: rewrite README and update project documentation

test: update tests for new module structure

chore: update Docker configuration for new structure

chore: create frontend placeholder directory

refactor: modularize backend into app/services flat layout

chore: restructure project into backend/frontend layout

docs: add README and documentation

test: add unit and e2e tests

chore: add Docker and deployment configuration

chore: add middleware, logging, and auth

feat: implement GUVI callback reporting