chore(deps): remove unused react-syntax-highlighter

react-syntax-highlighter (and its @types) is no longer imported anywhere —
code highlighting is handled by the Shiki web worker. Drop the dead deps.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

package.json

@@ -100,7 +100,6 @@
     "@radix-ui/react-slot": "^1.2.3",
     "@radix-ui/react-toggle": "^1.1.10",
     "@radix-ui/react-tooltip": "^1.2.8",
-    "@types/react-syntax-highlighter": "^15.5.13",
     "@xenova/transformers": "^2.17.2",
     "@zumer/snapdom": "^2.12.8",
     "bun-pty": "^0.4.5",
@@ -115,7 +114,6 @@
     "react": "^19.1.1",
     "react-dom": "^19.1.1",
     "react-markdown": "^10.1.0",
-    "react-syntax-highlighter": "^15.6.6",
     "remark-gfm": "^4.0.1",
     "simple-git": "^3.28.0",
     "sonner": "^2.0.7",