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.Dynamic/StringCleaner.cs

@@ -0,0 +1,51 @@
+using HtmlAgilityPack;
+using Microsoft.Recognizers.Text.Number;
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+using System.Text;
+using System.Text.RegularExpressions;
+using System.Threading.Tasks;
+using System.Web;
+
+namespace Beam.Dynamic {
+    public static partial class StringCleaner {
+        [GeneratedRegex("&#x?[\\d\\w]{1,4};")]
+        public static partial Regex MochaBlendUnicodeEscapeSequence();
+
+        private static string UnicodeEscapeSequences(string text) {
+            return MochaBlendUnicodeEscapeSequence().Replace(text, (x) => {
+                int numOfDigits = x.Value.Length - 3;
+                int sequence = 0;
+                if (x.Value[2] == 'x')
+                    sequence = int.Parse(x.Value[3..(3 + (numOfDigits - 1))], System.Globalization.NumberStyles.HexNumber);
+                else
+                    sequence = int.Parse(x.Value[2..(2 + numOfDigits)]);
+                var uni = Encoding.Unicode.GetString(BitConverter.GetBytes(sequence));
+                return uni.Length == 1 ? uni : uni[0].ToString();
+            });
+        }
+
+        public static List<int> ParseNumbers(string text, string from) {
+            var results = NumberRecognizer.RecognizeNumber(text, from, NumberOptions.None, false);
+            var resolved = results.Select((x) => {
+                if (x.Resolution.TryGetValue("value", out var value) && double.TryParse(value.ToString(), out var number))
+                    return (int?)number;
+                return null;
+            })
+                .Where((x) => x.HasValue).ToList();
+            if (resolved.Count == 0)
+                return [];
+            return resolved.Select((x) => x!.Value).ToList();
+        }
+
+        public static string Clean(string? onlineText) {
+            if (string.IsNullOrWhiteSpace(onlineText))
+                return "";
+            var decoded = HttpUtility.HtmlDecode(onlineText);
+            var escaped = UnicodeEscapeSequences(onlineText);
+            return escaped;
+        }
+    }
+}