Application propre sans erreurs. Bonne base sur laquelle repartir de zero en cas de soucis majeurs.

lib/core/theme/app_theme.dart

@@ -0,0 +1,20 @@
+import 'package:flutter/material.dart';
+
+class AppTheme {
+  static final ThemeData lightTheme = ThemeData(
+    primaryColor: Colors.blue,
+    colorScheme: const ColorScheme.light(
+      secondary: Colors.orange,
+    ),
+    brightness: Brightness.light,
+    buttonTheme: const ButtonThemeData(buttonColor: Colors.blue),
+  );
+
+  static final ThemeData darkTheme = ThemeData(
+    primaryColor: Colors.black,
+    colorScheme: const ColorScheme.dark(
+      secondary: Colors.red,
+    ),
+    brightness: Brightness.dark,
+  );
+}