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

keep-notes/next.config.ts

@@ -1,11 +1,29 @@
 import type { NextConfig } from "next";
 import path from "path";
 
+const withPWA = require("@ducanh2912/next-pwa").default({
+  dest: "public",
+  register: true,
+  skipWaiting: true,
+  disable: process.env.NODE_ENV === "development",
+});
+
 const nextConfig: NextConfig = {
+  // Enable standalone output for Docker
+  output: 'standalone',
+
   turbopack: {
     // Set root to parent directory to support monorepo workspace structure
     root: path.resolve(__dirname, ".."),
   },
+
+  // Optimize for production
+  reactStrictMode: true,
+
+  // Image optimization
+  images: {
+    unoptimized: true, // Required for standalone
+  },
 };
 
-export default nextConfig;
+export default withPWA(nextConfig);