fix(i18n): drop unused video-control strings and restore spinner lookups

`clean_translations.py --strict` reported seven unused keys.

Three are genuinely dead: TrackSelectionHelper.getEmptyMessage was
removed as unreachable in 4307c49c, and the sheets that need an empty
state carry their own strings. Removes them from every locale.

The four accessibility keys are false positives. tv_number_spinner
aliased the subtree as `final a11y = ...accessibility`, which the static
scanner cannot follow — its docstring says as much. Binds the documented
`final t = Translations.of(context)` instead and hoists the two labels,
so the semantics stay identical and the scanner sees the chains.

lib/i18n/strings_da.g.dart

@@ -704,9 +704,6 @@ class _Translations$videoControls$da extends Translations$videoControls$en {
 	@override String get searchSubtitles => 'Søg undertekster';
 	@override String get language => 'Sprog';
 	@override String get noSubtitlesFound => 'Ingen undertekster fundet';
-	@override String get noSubtitlesAvailable => 'Ingen undertekster tilgængelige';
-	@override String get noAudioTracksAvailable => 'Ingen lydspor tilgængelige';
-	@override String get noTracksAvailable => 'Ingen spor tilgængelige';
 	@override String get subtitleDownloaded => 'Undertekst downloadet';
 	@override String get subtitleDownloadedNotApplied => 'Underteksten blev downloadet, men kunne ikke vælges';
 	@override String get subtitleDownloadFailed => 'Kunne ikke downloade undertekst';
@@ -2712,12 +2709,9 @@ extension on TranslationsDa {
 			'videoControls.searchSubtitles' => 'Søg undertekster',
 			'videoControls.language' => 'Sprog',
 			'videoControls.noSubtitlesFound' => 'Ingen undertekster fundet',
-			'videoControls.noSubtitlesAvailable' => 'Ingen undertekster tilgængelige',
+			'videoControls.subtitleDownloaded' => 'Undertekst downloadet',
 			_ => null,
 		} ?? switch (path) {
-			'videoControls.noAudioTracksAvailable' => 'Ingen lydspor tilgængelige',
-			'videoControls.noTracksAvailable' => 'Ingen spor tilgængelige',
-			'videoControls.subtitleDownloaded' => 'Undertekst downloadet',
 			'videoControls.subtitleDownloadedNotApplied' => 'Underteksten blev downloadet, men kunne ikke vælges',
 			'videoControls.subtitleDownloadFailed' => 'Kunne ikke downloade undertekst',
 			'videoControls.searchLanguages' => 'Søg sprog...',
@@ -3227,11 +3221,11 @@ extension on TranslationsDa {
 			'watchTogether.codeMustBe5Chars' => 'Sessionskode skal være 5 tegn',
 			'watchTogether.joinInstructions' => 'Indtast værtens sessionskode for at deltage.',
 			'watchTogether.failedToCreate' => 'Kunne ikke oprette session',
-			_ => null,
-		} ?? switch (path) {
 			'watchTogether.failedToJoin' => 'Kunne ikke deltage i session',
 			'watchTogether.sessionCodeCopied' => 'Sessionskode kopieret til udklipsholder',
 			'watchTogether.relayUnreachable' => 'Relayserveren kan ikke nås. Blokering hos internetudbyderen kan forhindre Se sammen.',
+			_ => null,
+		} ?? switch (path) {
 			'watchTogether.reconnectingToHost' => 'Genopretter forbindelse til vært...',
 			'watchTogether.currentPlayback' => 'Nuværende afspilning',
 			'watchTogether.joinCurrentPlayback' => 'Deltag i nuværende afspilning',