chore(deps): react-markdown 10

react-markdown 10 removed the `className` prop and no longer renders a
wrapper element; passing className now throws at render time. Each of the
three call sites gets an explicit wrapping div carrying the same classes,
which reproduces the v9 DOM exactly.

The large diff is re-indentation from the added wrapper. `git diff -w`
shows the only substantive change per file is the moved className.

Fixes the 19 tests that failed on the upgrade. 598 tests pass, build clean,
lint unchanged.

frontend/package.json

@@ -52,7 +52,7 @@
     "react-force-graph-2d": "^1.29.1",
     "react-google-drive-picker": "^1.2.2",
     "react-i18next": "^17.0.13",
-    "react-markdown": "^9.1.0",
+    "react-markdown": "^10.1.0",
     "react-redux": "^9.3.0",
     "react-router-dom": "^7.18.3",
     "react-syntax-highlighter": "^16.1.1",