Add SQL, Erlang, and Forth highlighter implementations and tests for LSP process and transport handling.

- Added highlighters for new languages (SQL, Erlang, Forth) with filetype recognition.
- Updated and reorganized syntax files to maintain consistency and modularity.
- Introduced LSP transport framing unit tests and JSON decoding/dispatch tests.
- Refactored `LspManager`, integrating UTF-16/UTF-8 position conversions and robust diagnostics handling.
- Enhanced server start/restart logic with workspace root detection and logging to improve LSP usability.

GUIFrontend.cc

@@ -16,8 +16,8 @@
 #include "Font.h" // embedded default font (DefaultFontRegular)
 #include "GUIConfig.h"
 #include "GUITheme.h"
-#include "HighlighterRegistry.h"
-#include "NullHighlighter.h"
+#include "syntax/HighlighterRegistry.h"
+#include "syntax/NullHighlighter.h"
 
 
 #ifndef KTE_FONT_SIZE