Create QR code generation script

[magush27]

Create a Node.js script to generate QR codes for Cboard Access codes.

File: scripts/generate-qr.js

Tasks:

• Add qrcode npm dependency
• Create script accepting code and optional base URL arguments
• Generate PNG file with 400px width
• Output filename and encoded URL

Example of usage: node scripts/generate-qr.js CAFE01 https://app.cboard.io