Enhance group member management: add last name support in GroupMember model, update member display in chat and trip details, and implement pseudo change functionality in chat group.

lib/models/group_member.dart

@@ -1,6 +1,7 @@
 class GroupMember {
   final String userId;
   final String firstName;
+  final String lastName;
   final String pseudo; // Pseudo du membre (par défaut = prénom)
   final String role; // 'admin' ou 'member'
   final DateTime joinedAt;
@@ -9,17 +10,20 @@ class GroupMember {
   GroupMember({
     required this.userId,
     required this.firstName,
+    String? lastName,
     String? pseudo,
     this.role = 'member',
     DateTime? joinedAt,
     this.profilePictureUrl,
-  })  : pseudo = pseudo ?? firstName, // Par défaut, pseudo = prénom
+  })  : lastName = lastName ?? '',
+        pseudo = pseudo ?? firstName,
         joinedAt = joinedAt ?? DateTime.now();
 
   factory GroupMember.fromMap(Map<String, dynamic> map, String userId) {
     return GroupMember(
       userId: userId,
       firstName: map['firstName'] ?? '',
+      lastName: map['lastName'] ?? '',
       pseudo: map['pseudo'] ?? map['firstName'] ?? '',
       role: map['role'] ?? 'member',
       joinedAt: DateTime.fromMillisecondsSinceEpoch(map['joinedAt'] ?? 0),
@@ -30,6 +34,7 @@ class GroupMember {
   Map<String, dynamic> toMap() {
     return {
       'firstName': firstName,
+      'lastName': lastName,
       'pseudo': pseudo,
       'role': role,
       'joinedAt': joinedAt.millisecondsSinceEpoch,
@@ -40,6 +45,7 @@ class GroupMember {
   GroupMember copyWith({
     String? userId,
     String? firstName,
+    String? lastName,
     String? pseudo,
     String? role,
     DateTime? joinedAt,
@@ -48,6 +54,7 @@ class GroupMember {
     return GroupMember(
       userId: userId ?? this.userId,
       firstName: firstName ?? this.firstName,
+      lastName: lastName ?? this.lastName,
       pseudo: pseudo ?? this.pseudo,
       role: role ?? this.role,
       joinedAt: joinedAt ?? this.joinedAt,