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/prisma/migrations/20260104105155_add_images/migration.sql

@@ -0,0 +1,2 @@
+-- AlterTable
+ALTER TABLE "Note" ADD COLUMN "images" TEXT;