Login screen (with a language picker), header, account menu, sync status, About and
Release Notes dialogs, and the version banner are now fully translated in Hungarian,
English and German.
About (in the account menu) shows frontend/backend/database versions + build.
Release Notes renders per-version highlights with a commit-SHA reference; a
dismissible banner appears once after the running build's version changes and
links into the notes. Adds a reusable Modal shell and the release-notes data
(detailed v0.1.0).