Fix issue #534: Modernization and refactoring: C# codebase does not leverage latest C# features

[ngtduc693]

• I have performed a self-review of my code
• My code follows the style guidelines of this project
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Comments in areas I changed are up to date
• I have added comments to hard-to-understand areas of my code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.62%. Comparing base (79497a6) to head (d746a24).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #535   +/-   ##
=======================================
  Coverage   96.62%   96.62%           
=======================================
  Files         274      274           
  Lines       10835    10824   -11     
  Branches     1535     1534    -1     
=======================================
- Hits        10469    10459   -10     
  Misses        232      232           
+ Partials      134      133    -1     

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[Copilot]

Pull Request Overview

This PR modernizes the C# codebase by leveraging newer C# language features to improve code conciseness and performance. The changes replace verbose traditional syntax with more modern, idiomatic C# patterns.

• Replaces verbose LINQ operations with more efficient single-method calls
• Converts multi-line constructors to concise expression-bodied members using tuple deconstruction
• Refactors complex conditional logic into ternary expressions and adds performance optimizations using Span

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
DataStructures/Timeline.cs	Simplified event removal using RemoveAll instead of Where/ToList/foreach pattern
DataStructures/BinarySearchTree/BinarySearchTree.cs	Converted constructors to expression-bodied members with tuple deconstruction
Algorithms/Other/Luhn.cs	Refactored conditional logic to ternary expressions and added Span optimization with input validation
Algorithms.Tests/Other/LuhnTests.cs	Added comprehensive edge case testing for the modernized Luhn algorithm

Comments suppressed due to low confidence (1)

Algorithms/Other/Luhn.cs:1

• The test replaces 'x' with '0' but GetLostNum expects the input to contain 'x' to find the missing digit. This test doesn't validate the actual GetLostNum functionality since it removes the 'x' character that the method is designed to process.

namespace Algorithms.Other;

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[siriak]

Looks good, thanks!