feat: Implement room login state management and enhance SAR message handling

lib/models/room_login_state.dart

@@ -0,0 +1,111 @@
+import 'dart:typed_data';
+
+/// Represents the login state for a room
+class RoomLoginState {
+  final Uint8List publicKeyPrefix;
+  final bool isLoggedIn;
+  final bool isAdmin;
+  final int permissions;
+  final int? tag;
+  final DateTime? loginTime;
+  final bool hasPassword; // Whether we have a saved password
+
+  const RoomLoginState({
+    required this.publicKeyPrefix,
+    this.isLoggedIn = false,
+    this.isAdmin = false,
+    this.permissions = 0,
+    this.tag,
+    this.loginTime,
+    this.hasPassword = false,
+  });
+
+  /// Create a logged-in state
+  factory RoomLoginState.loggedIn({
+    required Uint8List publicKeyPrefix,
+    required int permissions,
+    required bool isAdmin,
+    required int tag,
+    required bool hasPassword,
+  }) {
+    return RoomLoginState(
+      publicKeyPrefix: publicKeyPrefix,
+      isLoggedIn: true,
+      isAdmin: isAdmin,
+      permissions: permissions,
+      tag: tag,
+      loginTime: DateTime.now(),
+      hasPassword: hasPassword,
+    );
+  }
+
+  /// Create a logged-out state
+  factory RoomLoginState.loggedOut({
+    required Uint8List publicKeyPrefix,
+    bool hasPassword = false,
+  }) {
+    return RoomLoginState(
+      publicKeyPrefix: publicKeyPrefix,
+      isLoggedIn: false,
+      hasPassword: hasPassword,
+    );
+  }
+
+  /// Copy with modified fields
+  RoomLoginState copyWith({
+    Uint8List? publicKeyPrefix,
+    bool? isLoggedIn,
+    bool? isAdmin,
+    int? permissions,
+    int? tag,
+    DateTime? loginTime,
+    bool? hasPassword,
+  }) {
+    return RoomLoginState(
+      publicKeyPrefix: publicKeyPrefix ?? this.publicKeyPrefix,
+      isLoggedIn: isLoggedIn ?? this.isLoggedIn,
+      isAdmin: isAdmin ?? this.isAdmin,
+      permissions: permissions ?? this.permissions,
+      tag: tag ?? this.tag,
+      loginTime: loginTime ?? this.loginTime,
+      hasPassword: hasPassword ?? this.hasPassword,
+    );
+  }
+
+  /// Get formatted public key prefix (e.g., "15:59:89:54:b4:d4")
+  String get publicKeyPrefixHex {
+    return publicKeyPrefix
+        .map((b) => b.toRadixString(16).padLeft(2, '0'))
+        .join(':');
+  }
+
+  /// Get login duration if logged in
+  Duration? get loginDuration {
+    if (!isLoggedIn || loginTime == null) return null;
+    return DateTime.now().difference(loginTime!);
+  }
+
+  /// Get formatted login duration (e.g., "2h 15m ago")
+  String? get loginDurationFormatted {
+    final duration = loginDuration;
+    if (duration == null) return null;
+
+    if (duration.inMinutes < 1) {
+      return 'just now';
+    } else if (duration.inMinutes < 60) {
+      return '${duration.inMinutes}m ago';
+    } else if (duration.inHours < 24) {
+      final hours = duration.inHours;
+      final minutes = duration.inMinutes % 60;
+      return minutes > 0 ? '${hours}h ${minutes}m ago' : '${hours}h ago';
+    } else {
+      final days = duration.inDays;
+      return '${days}d ago';
+    }
+  }
+
+  @override
+  String toString() {
+    return 'RoomLoginState(prefix: $publicKeyPrefixHex, loggedIn: $isLoggedIn, admin: $isAdmin, hasPassword: $hasPassword)';
+  }
+}