Replace the modal About dialog with an embedded About page and introduce
a three-pane desktop layout: persistent sidebar navigation, flat station
list, right-side details panel, and compact player bar.
Load the GPLv3 license text from C++ and expose it to QML as context
data. Normalize i18n source strings to English, complete German and
Russian translations (133 strings each), and centralize page navigation
helpers in Main.qml. Simplify compact HeaderNavigation and extend
.gitignore for local build artifacts.
Phase 2 splits the remaining large Main.qml blocks into StationCard,
WorldCategories, WorldCategoryHeader, PlayerBar, and AboutDialog.
Main.qml is now ~414 lines (down from ~1240); behavior unchanged.
