fix: resolve all compile errors from Stitch theme merge

- Add missing AppTheme animation constants (durationSm/Md/Lg/Xl, curveSmooth)
  to satisfy remote widget references.
- Replace deprecated GlassContainer(opacity:) with .glass()/.floating()/.base()
  in login_screen, live_tv_tab, mobile_live_tv_tab, player_screen,
  dashboard_screen.
- Fix const-eval errors by removing const from BorderSide/Text/BoxDecoration
  using AppColors.focusColor and AppColors.border (runtime getters).
- Fix subtitle_service.dart: padEnd → padRight (Dart String API).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

lib/features/iptv/services/subtitle_service.dart

@@ -170,7 +170,7 @@ class SubtitleService {
     final minutes = int.parse(parts[1]);
     final secondsParts = parts[2].split('.');
     final seconds = int.parse(secondsParts[0]);
-    final milliseconds = int.parse(secondsParts[1].padEnd(3, '0'));
+    final milliseconds = int.parse(secondsParts[1].padRight(3, '0'));
 
     return Duration(
       hours: hours,