feat: introduce IPTV player, GoRouter setup, themed loading screen, and content tabs

lib/core/widgets/themed_loading_screen.dart

@@ -0,0 +1,29 @@
+import 'package:flutter/material.dart';
+import '../theme/app_colors.dart';
+
+class ThemedLoading extends StatelessWidget {
+  const ThemedLoading({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return Container(
+      decoration: const BoxDecoration(
+        gradient: RadialGradient(
+          center: Alignment(0, -0.2),
+          radius: 1.5,
+          colors: [
+            Color(0xFF2C2C2E),
+            Color(0xFF000000),
+          ],
+          stops: [0.0, 1.0],
+        ),
+      ),
+      child: const Center(
+        child: CircularProgressIndicator(
+          color: Colors.white,
+          strokeWidth: 3,
+        ),
+      ),
+    );
+  }
+}