Advance sprint 4 chat parity and message UX

Expand IRCv3 chat history, notice routing, CTCP handling,
and message interactions with richer rendering and tests.

Author: r0073rr0r

lib/core/models/app_settings.dart

@@ -1,27 +1,49 @@
+enum NoticeRoutingMode { server, active, notice, private }
+
 class AppSettings {
   const AppSettings({
     this.showRawEvents = true,
+    this.noticeRouting = NoticeRoutingMode.server,
+    this.showHeaderSearchButton = true,
+    this.showAttachmentPreviews = true,
   });
 
   final bool showRawEvents;
+  final NoticeRoutingMode noticeRouting;
+  final bool showHeaderSearchButton;
+  final bool showAttachmentPreviews;
 
   AppSettings copyWith({
     bool? showRawEvents,
+    NoticeRoutingMode? noticeRouting,
+    bool? showHeaderSearchButton,
+    bool? showAttachmentPreviews,
   }) {
     return AppSettings(
       showRawEvents: showRawEvents ?? this.showRawEvents,
+      noticeRouting: noticeRouting ?? this.noticeRouting,
+      showHeaderSearchButton: showHeaderSearchButton ?? this.showHeaderSearchButton,
+      showAttachmentPreviews: showAttachmentPreviews ?? this.showAttachmentPreviews,
     );
   }
 
   Map<String, Object?> toJson() {
     return {
       'showRawEvents': showRawEvents,
+      'noticeRouting': noticeRouting.name,
+      'showHeaderSearchButton': showHeaderSearchButton,
+      'showAttachmentPreviews': showAttachmentPreviews,
     };
   }
 
   factory AppSettings.fromJson(Map<String, Object?> json) {
     return AppSettings(
       showRawEvents: (json['showRawEvents'] as bool?) ?? true,
+      noticeRouting: json['noticeRouting'] is String
+          ? NoticeRoutingMode.values.byName(json['noticeRouting']! as String)
+          : NoticeRoutingMode.server,
+      showHeaderSearchButton: (json['showHeaderSearchButton'] as bool?) ?? true,
+      showAttachmentPreviews: (json['showAttachmentPreviews'] as bool?) ?? true,
     );
   }
 }

lib/core/models/irc_message.dart

@@ -7,6 +7,8 @@ class IrcMessage {
     required this.sender,
     required this.content,
     required this.timestamp,
+    this.tags = const <String, String?>{},
+    this.isPlayback = false,
     this.isOwn = false,
     this.kind = IrcMessageKind.chat,
   });
@@ -16,6 +18,8 @@ class IrcMessage {
   final String sender;
   final String content;
   final DateTime timestamp;
+  final Map<String, String?> tags;
+  final bool isPlayback;
   final bool isOwn;
   final IrcMessageKind kind;
 
@@ -26,6 +30,8 @@ class IrcMessage {
       'sender': sender,
       'content': content,
       'timestamp': timestamp.toIso8601String(),
+      'tags': tags,
+      'isPlayback': isPlayback,
       'isOwn': isOwn,
       'kind': kind.name,
     };
@@ -38,6 +44,8 @@ class IrcMessage {
       sender: json['sender']! as String,
       content: json['content']! as String,
       timestamp: DateTime.parse(json['timestamp']! as String),
+      tags: Map<String, String?>.from((json['tags'] as Map?) ?? const <String, String?>{}),
+      isPlayback: (json['isPlayback'] as bool?) ?? false,
       isOwn: (json['isOwn'] as bool?) ?? false,
       kind: IrcMessageKind.values.byName(
         (json['kind'] as String?) ?? IrcMessageKind.chat.name,