fix(editor): convert pasted markdown to formatted content (#498)

The tiptap-markdown extension was registered with default config, where
`transformPastedText` defaults to false. As a result, pasting markdown
text into card descriptions resulted in literal characters (e.g. '# heading'
shown as a paragraph of text) rather than rendered formatting.

Typing markdown shortcuts in the editor already worked because that goes
through a different path. Programmatic writes via the API also work
because they bypass the editor entirely. Only paste was affected.

Enabling `transformPastedText: true` makes pasted markdown behave as
users intuitively expect, matching the typed-markdown UX.

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

apps/web/src/components/Editor.tsx

@@ -474,7 +474,7 @@ export default function Editor({
           autolink: true,
           linkOnPaste: true,
         }),
-        Markdown,
+        Markdown.configure({ transformPastedText: true }),
         Placeholder.configure({
           placeholder: readOnly
             ? ""