fix: Add debounced Undo/Redo system to avoid character-by-character history

- Add debounced state updates for title and content (500ms delay)
- Immediate UI updates with delayed history saving
- Prevent one-letter-per-undo issue
- Add cleanup for debounce timers on unmount

keep-notes/lib/prisma.ts

@@ -0,0 +1,15 @@
+import { PrismaClient } from '@prisma/client'
+
+const prismaClientSingleton = () => {
+  return new PrismaClient()
+}
+
+declare const globalThis: {
+  prismaGlobal: ReturnType<typeof prismaClientSingleton>;
+} & typeof global;
+
+const prisma = globalThis.prismaGlobal ?? prismaClientSingleton()
+
+export default prisma
+
+if (process.env.NODE_ENV !== 'production') globalThis.prismaGlobal = prisma