feat(ui): écran Création/édition de programme

Ajoute l'écran de programme (presentation/program_screen.dart) et un
écran d'accueil (presentation/home_screen.dart) pour la navigation,
avec les ajustements application/domaine/repositories nécessaires.
flutter analyze propre, 11/11 tests verts, build APK debug validé.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lib/presentation/home_screen.dart

@@ -0,0 +1,48 @@
+import 'package:flutter/material.dart';
+
+import '../application/app_bootstrap.dart';
+import 'exercise_library_screen.dart';
+import 'program_screen.dart';
+
+final class HomeScreen extends StatelessWidget {
+  const HomeScreen({required this.bootstrap, super.key});
+
+  final AppBootstrap bootstrap;
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(title: const Text('GameTime')),
+      body: ListView(
+        children: [
+          ListTile(
+            leading: const Icon(Icons.fitness_center),
+            title: const Text('Exercices'),
+            trailing: const Icon(Icons.chevron_right),
+            onTap: () => Navigator.of(context).push(
+              MaterialPageRoute(
+                builder: (context) => ExerciseLibraryScreen(
+                  exerciseUseCases: bootstrap.exerciseUseCases,
+                  mediaUseCases: bootstrap.mediaUseCases,
+                ),
+              ),
+            ),
+          ),
+          ListTile(
+            leading: const Icon(Icons.list_alt),
+            title: const Text('Programmes'),
+            trailing: const Icon(Icons.chevron_right),
+            onTap: () => Navigator.of(context).push(
+              MaterialPageRoute(
+                builder: (context) => ProgramListScreen(
+                  programUseCases: bootstrap.programUseCases,
+                  exerciseUseCases: bootstrap.exerciseUseCases,
+                ),
+              ),
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+}