reorder file structure

Frontend/lib/mih_objects/session_st.dart

@@ -1,23 +0,0 @@
-class SessionST {
-  final String status;
-  final bool exists;
-
-  const SessionST({
-    required this.status,
-    required this.exists,
-  });
-
-  factory SessionST.fromJson(Map<String, dynamic> json) {
-    return switch (json) {
-      {
-        'status': String status,
-        'exists': bool exists,
-      } =>
-        SessionST(
-          status: status,
-          exists: exists,
-        ),
-      _ => throw const FormatException('Failed to load SessionST.'),
-    };
-  }
-}