feat: Refactor project structure and add core library

- Migrate shared components from WPF to a new Core library.
- Introduce GroupInfo, M3UInfo, and ObservableViewModelBase classes.
- Implement M3UParser for downloading and parsing M3U files.
- Add ProgramsData for managing program lists and guides.
- Create SettingsModel for application settings management.
- Update project references in solution files.

TV Player Core/ObservableViewModelBase.cs

@@ -0,0 +1,28 @@
+using System.ComponentModel;
+using System.Runtime.CompilerServices;
+
+namespace TV_Player
+{
+    public abstract class ObservableViewModelBase : INotifyPropertyChanged
+    {
+        public event PropertyChangedEventHandler PropertyChanged;
+
+        protected void RaisePropertyChanged(string propertyName)
+            => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+
+        /// <summary>
+        /// Set a property and raise a property changed event if it has changed
+        /// </summary>
+        protected bool SetProperty<T>(ref T property, T value, [CallerMemberName] string propertyName = null)
+        {
+            if (EqualityComparer<T>.Default.Equals(property, value))
+            {
+                return false;
+            }
+
+            property = value;
+            RaisePropertyChanged(propertyName);
+            return true;
+        }
+    }
+}