feat: replace mail protocol with smolmail and rebuild the UI

lib/shared/utils/format.dart

@@ -0,0 +1,37 @@
+import "package:flutter/material.dart";
+import "package:flutter/services.dart";
+import "package:intl/intl.dart";
+
+/// One path for all replies so the Re: rule lives once.
+String replySubject(String subject) =>
+    subject.isEmpty || subject.startsWith("Re:") ? subject : "Re: $subject";
+
+String formatTime(int? seconds) {
+  if (seconds == null) return "";
+  final date = DateTime.fromMillisecondsSinceEpoch(seconds * 1000, isUtc: true);
+  return DateFormat.yMMMMd().add_jm().format(date.toLocal());
+}
+
+/// The full date is too wide for a list row's trailing slot — this is what
+/// message_tile.dart shows instead: just a time for today, else a short date.
+String formatShortTime(int? seconds) {
+  if (seconds == null) return "";
+  final date =
+      DateTime.fromMillisecondsSinceEpoch(seconds * 1000, isUtc: true).toLocal();
+  final now = DateTime.now();
+  if (date.year == now.year && date.month == now.month && date.day == now.day) {
+    return DateFormat.jm().format(date);
+  }
+  if (date.year == now.year) {
+    return DateFormat.MMMd().format(date);
+  }
+  return DateFormat.yMd().format(date);
+}
+
+Future<void> copyText(BuildContext context, String text) async {
+  await Clipboard.setData(ClipboardData(text: text));
+  if (context.mounted) {
+    ScaffoldMessenger.of(context)
+        .showSnackBar(const SnackBar(content: Text("Copied to clipboard")));
+  }
+}