change context diagram to png format

Author: datpham0412

README.md

@@ -324,7 +324,7 @@ _Pure business entities with no external dependencies:_
 By following Clean Architecture, MatchFlow achieves high testability, clear module boundaries, and the ability to swap out or mock any external dependency (databases, cloud services, UI) without impacting the business core.
 
 
-![Context Diagram](/frontend/public/context_diagram.svg)
+![Context Diagram](/frontend/public/context_diagram.png)
 
 ##  Screenshots
 ###  Authentication