fix(editor): scale code block font size with editor zoom (#208)

Code blocks used a hardcoded 13px font-size instead of scaling with --editor-font-size, so they didn't resize with the rest of the editor content when zooming.

Reviewed-on: https://codeberg.org/ArkHost/HelixNotes/pulls/208

src/lib/components/Editor.svelte

@@ -8363,7 +8363,7 @@
 		overflow-x: auto;
 		background: none;
 		padding: 0;
-		font-size: 13px;
+		font-size: 0.93em;
 		line-height: 1.5;
 	}