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/schema.prisma

@@ -0,0 +1,31 @@
+// This is your Prisma schema file,
+// learn more about it in the docs: https://pris.ly/d/prisma-schema
+
+generator client {
+  provider = "prisma-client-js"
+}
+
+datasource db {
+  provider = "sqlite"
+  url      = env("DATABASE_URL")
+}
+
+model Note {
+  id          String   @id @default(cuid())
+  title       String?
+  content     String
+  color       String   @default("default")
+  isPinned    Boolean  @default(false)
+  isArchived  Boolean  @default(false)
+  type        String   @default("text") // "text" or "checklist"
+  checkItems  String?  // For checklist items stored as JSON string
+  labels      String?  // Array of label names stored as JSON string
+  images      String?  // Array of image URLs stored as JSON string
+  order       Int      @default(0)
+  createdAt   DateTime @default(now())
+  updatedAt   DateTime @updatedAt
+
+  @@index([isPinned])
+  @@index([isArchived])
+  @@index([order])
+}