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/TV Player Core.csproj

@@ -0,0 +1,17 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Library</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <RootNamespace>TV_Player</RootNamespace>
+    <AssemblyName>TV Player Core</AssemblyName>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Newtonsoft.Json" Version="13.0.4" />
+    <PackageReference Include="System.Reactive" Version="6.0.2" />
+  </ItemGroup>
+
+</Project>