Drop nested NavigationStack, .searchable, and close button from the
PeerTube explore view on tvOS; use an inline search field plus Filters
button so focus separates cleanly and the sidebar title is no longer
overlapped. Keep the header visible across empty/error states so the
query can be cleared. Hide the filters and scan-network sheet toolbars
on tvOS, apply filter changes immediately, and add padding plus
scrollClipDisabled so focused rows aren't clipped.
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.
