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/app/api/labels/route.ts

@@ -0,0 +1,30 @@
+import { NextRequest, NextResponse } from 'next/server'
+import prisma from '@/lib/prisma'
+
+// GET /api/labels - Get all unique labels
+export async function GET(request: NextRequest) {
+  try {
+    const notes = await prisma.note.findMany({
+      select: { labels: true }
+    })
+
+    const labelsSet = new Set<string>()
+    notes.forEach(note => {
+      const labels = note.labels ? JSON.parse(note.labels) : null
+      if (labels) {
+        labels.forEach((label: string) => labelsSet.add(label))
+      }
+    })
+
+    return NextResponse.json({
+      success: true,
+      data: Array.from(labelsSet).sort()
+    })
+  } catch (error) {
+    console.error('GET /api/labels error:', error)
+    return NextResponse.json(
+      { success: false, error: 'Failed to fetch labels' },
+      { status: 500 }
+    )
+  }
+}