Refactor database layer: convert to DatabaseProvider class with initialization

bin/models/geoposition.dart

@@ -0,0 +1,41 @@
+class Geoposition {
+  final int id;
+  final int userId;
+  final double xValue;
+  final double yValue;
+  final DateTime datetime;
+  final Duration lifetime;
+  final DateTime expiresAt;
+  
+  Geoposition({
+    required this.id,
+    required this.userId,
+    required this.xValue,
+    required this.yValue,
+    required this.datetime,
+    required this.lifetime,
+    required this.expiresAt,
+  });
+  
+  Map<String, dynamic> toJson() {
+    return {
+      'id': id,
+      'x': xValue,
+      'y': yValue,
+      'datetime': datetime.toIso8601String(),
+      'remainingSeconds': expiresAt.difference(DateTime.now()).inSeconds,
+    };
+  }
+  
+  factory Geoposition.fromMap(Map<String, dynamic> map) {
+    return Geoposition(
+      id: map['id'],
+      userId: map['user_id'],
+      xValue: map['x_value'].toDouble(),
+      yValue: map['y_value'].toDouble(),
+      datetime: map['datetime'] as DateTime,
+      lifetime: Duration(seconds: map['lifetime']),
+      expiresAt: map['expires_at'] as DateTime,
+    );
+  }
+}