feat: add QR code generation script for seeded zones

Adds scripts/generate-qr.ts that generates one 400px PNG per warehouse
zone into public/qr/ (gitignored). Encodes /report?zone=<token> URL per
zone using NEXT_PUBLIC_APP_URL (default http://localhost:3000). Adds
public/qr/.gitkeep so the output directory is tracked. All 8 tests pass.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AWxyMibCuGGtSQSqfajDQ7

scripts/generate-qr.ts

@@ -0,0 +1,38 @@
+// scripts/generate-qr.ts
+import QRCode from 'qrcode'
+import { mkdirSync } from 'fs'
+import path from 'path'
+
+const BASE_URL = process.env.NEXT_PUBLIC_APP_URL ?? 'http://localhost:3000'
+
+// Matches seeded zone qr_code_token values in 20260709000008_seed.sql
+const ZONES = [
+  { token: 'scw1-dock-a-qr-2026',        name: 'SCW1 — Dock A' },
+  { token: 'scw1-cold-storage-qr-2026',  name: 'SCW1 — Cold Storage' },
+  { token: 'scw1-loading-bay-qr-2026',   name: 'SCW1 — Loading Bay' },
+]
+
+async function main() {
+  const outDir = path.join(process.cwd(), 'public', 'qr')
+  mkdirSync(outDir, { recursive: true })
+
+  for (const zone of ZONES) {
+    const url = `${BASE_URL}/report?zone=${zone.token}`
+    const outputPath = path.join(outDir, `${zone.token}.png`)
+
+    await QRCode.toFile(outputPath, url, {
+      width: 400,
+      margin: 2,
+      color: { dark: '#000000', light: '#FFFFFF' },
+    })
+
+    console.log(`✓ ${zone.name}`)
+    console.log(`  → ${url}`)
+    console.log(`  → ${outputPath}`)
+  }
+}
+
+main().catch((err) => {
+  console.error(err)
+  process.exit(1)
+})