feat: better and centralized loading screen

lib/ui/core/ui/await_loading.dart

@@ -0,0 +1,47 @@
+import 'dart:async';
+
+import 'package:flutter/material.dart';
+
+class AwaitLoading extends StatefulWidget {
+  const AwaitLoading({super.key});
+
+  @override
+  State<AwaitLoading> createState() => _AwaitLoadingState();
+}
+
+class _AwaitLoadingState extends State<AwaitLoading> {
+  String text = "";
+
+  Timer? t;
+
+  @override
+  void dispose() {
+    t?.cancel();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    t = Timer(Duration(seconds: 8), () {
+      setState(() {
+        text =
+            "Il semblerait qu'il y ait un problème. Vérifiez que vous êtes connecté·e à internet.";
+      });
+    });
+
+    return Column(
+      children: [
+        Expanded(child: SizedBox()),
+        Center(child: CircularProgressIndicator()),
+        Expanded(
+          child: Center(
+            child: SizedBox(
+              width: 300,
+              child: Text(text, textAlign: TextAlign.center),
+            ),
+          ),
+        ),
+      ],
+    );
+  }
+}

lib/ui/core/ui/overlay_boundary.dart

@@ -0,0 +1,27 @@
+import 'package:flutter/material.dart';
+
+class OverlayBoundary extends StatefulWidget {
+  const OverlayBoundary({super.key, required this.child});
+
+  final Widget child;
+
+  @override
+  State<OverlayBoundary> createState() => _OverlayBoundaryState();
+}
+
+class _OverlayBoundaryState extends State<OverlayBoundary> {
+  late final OverlayEntry _overlayEntry = OverlayEntry(
+    builder: (context) => widget.child,
+  );
+
+  @override
+  void didUpdateWidget(covariant OverlayBoundary oldWidget) {
+    super.didUpdateWidget(oldWidget);
+    _overlayEntry.markNeedsBuild();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Overlay(initialEntries: [_overlayEntry]);
+  }
+}