refactor: modularize Beam into new projects and interfaces

- Introduced modularity by splitting Beam into new projects: Beam.Abstractions, Beam.Models, and Beam.Downloaders.
- Refactored existing classes into appropriate namespaces and projects.
- Replaced specific implementations with abstractions (e.g., SourceLinkBuilder to LinkBuilder, State to IState, etc.).
- Updated interfaces: added ITemplate, IArticleData, IDownloadReport, and others for improved extensibility.
- Removed deprecated classes like SourceLinkBuilder and StateChangerFactory.
- Enhanced link handling in downloaders by refactoring to use `string` over `SourceLink`.
- Consolidated shared logic under Beam.Abstractions.

Beam.Abstractions/IDataBindings.cs

@@ -0,0 +1,27 @@
+using Beam.Dynamic;
+
+namespace Beam.Abstractions;
+
+public interface IDataBindings {
+    IDataProvider<string>? Title { get; set; }
+    IDataProvider<string[]>? Authors { get; set; }
+    IDataProvider<string>? Description { get; set; }
+    IDataProvider<string>? Content { get; set; }
+    IDataProvider<string[]>? Language { get; set; }
+    IDataProvider<string[]>? Tags { get; set; }
+    IDataProvider<string>? Publisher { get; set; }
+    IDataProvider<DateTimeOffset>? PublicationDate { get; set; }
+    IDataProvider<string>? ISBN { get; set; }
+    IDataProvider<int>? PageCount { get; set; }
+    IDataProvider<string>? CoverImage { get; set; }
+    IDataProvider<string[]>? Series { get; set; }
+    IDataProvider<int>? Edition { get; set; }
+    IDataProvider<string[]>? Contributors { get; set; }
+    IDataProvider<string[]>? Subjects { get; set; }
+    IDataProvider<string>? Rights { get; set; }
+    IDataProvider<string[]>? TableOfContents { get; set; }
+    IDataProvider<string[]>? PagesDropDown { get; set; }
+    IDataProvider<string>? NextPageButton { get; set; }
+    IDataProvider<string>? PreviousPageButton { get; set; }
+    Dictionary<string, IDataProvider?> Providers { get; set; }
+}