feat: set mermaid theme based on computed color scheme (#1397)

Use Mantine's `useComputedColorScheme` hook to dynamically configure mermaid's theme.
- When the computed color scheme is "light", the theme is set to "default".
- Otherwise, it is set to "dark".

apps/client/src/features/editor/components/code-block/mermaid-view.tsx

@@ -4,10 +4,14 @@ import mermaid from "mermaid";
 import { v4 as uuidv4 } from "uuid";
 import classes from "./code-block.module.css";
 import { useTranslation } from "react-i18next";
+import { useComputedColorScheme } from "@mantine/core";
+
+const computedColorScheme = useComputedColorScheme();
 
 mermaid.initialize({
   startOnLoad: false,
   suppressErrorRendering: true,
+  theme: computedColorScheme === "light" ? "default" : "dark",
 });
 
 interface MermaidViewProps {