fix: improve note interactions and markdown LaTeX support

## Bug Fixes

### Note Card Actions
- Fix broken size change functionality (missing state declaration)
- Implement React 19 useOptimistic for instant UI feedback
- Add startTransition for non-blocking updates
- Ensure smooth animations without page refresh
- All note actions now work: pin, archive, color, size, checklist

### Markdown LaTeX Rendering
- Add remark-math and rehype-katex plugins
- Support inline equations with dollar sign syntax
- Support block equations with double dollar sign syntax
- Import KaTeX CSS for proper styling
- Equations now render correctly instead of showing raw LaTeX

## Technical Details

- Replace undefined currentNote references with optimistic state
- Add optimistic updates before server actions for instant feedback
- Use router.refresh() in transitions for smart cache invalidation
- Install remark-math, rehype-katex, and katex packages

## Testing

- Build passes successfully with no TypeScript errors
- Dev server hot-reloads changes correctly

package.json.bak

@@ -0,0 +1,15 @@
+{
+  "name": "keep-workspace",
+  "private": true,
+  "workspaces": [
+    "keep-notes",
+    "mcp-server"
+  ],
+  "devDependencies": {
+    "tailwindcss": "^4",
+    "tw-animate-css": "^1.4.0"
+  },
+  "dependencies": {
+    "@prisma/client": "^5.22.0"
+  }
+}