feat: replace mail protocol with smolmail and rebuild the UI

lib/presentation/app_widget.dart

@@ -1,18 +1,53 @@
 import "package:flutter/material.dart";
 import "package:flutter_riverpod/flutter_riverpod.dart";
 
-import "package:flash_mail/presentation/theme/theme.dart";
-import "package:flash_mail/presentation/routes/app_router.dart";
+import "package:smol_mail/data/providers/providers.dart";
+import "package:smol_mail/presentation/theme/theme.dart";
+import "package:smol_mail/presentation/routes/app_router.dart";
 
-class AppWidget extends ConsumerWidget {
+/// SnackBars need no context through this key, so the client's trust
+/// warnings can be shown from anywhere in the protocol stack.
+final rootScaffoldMessengerKey = GlobalKey<ScaffoldMessengerState>();
+
+class AppWidget extends ConsumerStatefulWidget {
   const AppWidget({super.key});
 
   @override
-  Widget build(BuildContext context, WidgetRef ref) {
+  ConsumerState<AppWidget> createState() => _AppWidgetState();
+}
+
+class _AppWidgetState extends ConsumerState<AppWidget> {
+  @override
+  void initState() {
+    super.initState();
+    // §4/§8 trust warnings stay on screen until dismissed; ordinary notices
+    // do not use this channel.
+    ref.read(clientProvider).onWarning = (message) {
+      rootScaffoldMessengerKey.currentState?.showSnackBar(
+        SnackBar(
+          backgroundColor: const Color.fromRGBO(198, 40, 40, 1),
+          content: Text(message, style: const TextStyle(color: Colors.white)),
+          duration: const Duration(days: 1),
+          action: SnackBarAction(
+            label: "Dismiss",
+            textColor: Colors.white,
+            onPressed: () =>
+                rootScaffoldMessengerKey.currentState?.hideCurrentSnackBar(),
+          ),
+        ),
+      );
+    };
+  }
+
+  @override
+  Widget build(BuildContext context) {
     return MaterialApp.router(
-      title: "FlashMail",
-      theme: appTheme,
+      title: "kirakira",
+      theme: appThemeLight,
+      darkTheme: appThemeDark,
+      themeMode: ThemeMode.system,
       debugShowCheckedModeBanner: false,
+      scaffoldMessengerKey: rootScaffoldMessengerKey,
       routerConfig: AppRouter(ref).config(),
     );
   }