deleteConversation method
Deletes a conversation by its ID.
If the deleted conversation was the current one, the first remaining conversation becomes current, or null if none remain.
Implementation
void deleteConversation(final String conversationId) {
_conversations.removeWhere((final conv) => conv.id == conversationId);
if (_currentConversation?.id == conversationId) {
_currentConversation = _conversations.isNotEmpty
? _conversations.first
: null;
}
notifyListeners();
}