Use the tab root's top safe-area inset instead of a fixed 20pt, so the
search/options header in History and Bookmarks clears the floating "Home"
pill drawn by the sidebarAdaptable TabView.
On tvOS, ContentUnavailableView inside a Group doesn't expand to fill
available space — it sizes to content and aligns top-leading. Add
.frame(maxWidth: .infinity, maxHeight: .infinity) to all instances
so they center correctly in their parent containers.
Remove 32 non-dotted keys (16 unused format specifiers, 16 word keys)
and replace with properly namespaced dotted keys following the existing
convention (common.*, player.*, search.*).
