fix(ui): replace outer p tag with div in CustomCard to prevent invalid HTML nesting

[Vinit-786]

Fixes #653

Concisely describe the change

Replaced the outer <p id="cardBody-parsed"> wrapper with a <div> in src/components/ui/CustomCard/index.tsx.

Markdown renders ReactMarkdown, which outputs block-level elements such as <p> for markdown content. Wrapping it inside another <p> produces invalid nested paragraph markup. Using a <div> preserves valid HTML while allowing markdown content to render correctly.

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