chore: remove MUI and Emotion dependencies

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -20,11 +20,6 @@
     "test:e2e:headed": "playwright test --headed --config tests/playwright.config.ts"
   },
   "dependencies": {
-    "@emotion/react": "^11.14.0",
-    "@emotion/styled": "^11.14.1",
-    "@mui/icons-material": "^7.3.9",
-    "@mui/material": "^7.3.9",
-    "@mui/x-date-pickers": "^8.27.2",
     "@radix-ui/react-accordion": "^1.2.12",
     "@radix-ui/react-avatar": "^1.1.11",
     "@radix-ui/react-checkbox": "^1.3.3",