refactor: share focus chrome and simplify the TV picker and browse paths

Focus chrome was implemented twice, once in the focusable wrapper and once
in the focus builders; both now go through FocusChrome. TvColorPicker's
channel row was a copy of TvNumberSpinner and is now that widget in compact
density.

Also trims unused helpers and fields and simplifies the Jellyfin browse
paths.

lib/utils/content_utils.dart

@@ -26,17 +26,6 @@ class ContentTypeHelper {
 
   static bool isVideoContent(String type) => ContentTypes.videoTypes.contains(type.toLowerCase());
 
-  static bool isMusicLibrary(dynamic lib) {
-    if (lib == null) return false;
-    try {
-      // ignore: avoid_dynamic_calls — duck-typed across library shapes
-      final type = (lib as dynamic).kind?.id as String?;
-      return type?.toLowerCase() == ContentTypes.artist;
-    } catch (e) {
-      return false;
-    }
-  }
-
   static IconData getLibraryIcon(String type) {
     switch (type.toLowerCase()) {
       case ContentTypes.movie:

lib/utils/layout_constants.dart

@@ -18,12 +18,8 @@ class ScreenBreakpoints {
 
   static bool isTablet(double width) => width >= mobile && width < desktop;
 
-  static bool isWideTablet(double width) => width >= wideTablet && width < desktop;
-
   static bool isDesktop(double width) => width >= desktop && width < largeDesktop;
 
-  static bool isLargeDesktop(double width) => width >= largeDesktop;
-
   static bool isDesktopOrLarger(double width) => width >= desktop;
 
   static bool isWideTabletOrLarger(double width) => width >= wideTablet;

lib/utils/plex_cache_parser.dart

@@ -18,10 +18,4 @@ class PlexCacheParser {
     if (list == null || list.isEmpty) return null;
     return list.first as Map<String, dynamic>;
   }
-
-  static List<dynamic>? extractChapters(Map<String, dynamic>? cached) {
-    final metadata = extractFirstMetadata(cached);
-    if (metadata == null) return null;
-    return metadata['Chapter'] as List?;
-  }
 }