feat: scaffold Antonym fashion store

Anonymous Bitcoin-only fashion e-commerce with:
- Vue 3 + Tailwind 4 frontend with glassmorphism dark/light design system
- Express 5 + SQLite backend with BTCPay Server integration
- Nostr identity (NIP-07/keypair) for anonymous purchase tracking
- ChaCha20-Poly1305 encrypted shipping addresses
- Admin panel with order/product/stock management
- SVG logo splash animation with clip-path reveal
- 5 seeded products across 4 categories

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/lib/crypto.ts

@@ -0,0 +1,33 @@
+import crypto from 'node:crypto'
+
+const ALGORITHM = 'chacha20-poly1305'
+const NONCE_LENGTH = 12
+const TAG_LENGTH = 16
+
+function getKey(): Buffer {
+  const hex = process.env.ENCRYPTION_KEY
+  if (!hex || hex.length !== 64) {
+    throw new Error('ENCRYPTION_KEY must be a 64-character hex string (32 bytes)')
+  }
+  return Buffer.from(hex, 'hex')
+}
+
+export function encrypt(plaintext: string): string {
+  const key = getKey()
+  const nonce = crypto.randomBytes(NONCE_LENGTH)
+  const cipher = crypto.createCipheriv(ALGORITHM, key, nonce, { authTagLength: TAG_LENGTH })
+  const encrypted = Buffer.concat([cipher.update(plaintext, 'utf8'), cipher.final()])
+  const tag = cipher.getAuthTag()
+  return Buffer.concat([nonce, tag, encrypted]).toString('hex')
+}
+
+export function decrypt(ciphertext: string): string {
+  const key = getKey()
+  const buf = Buffer.from(ciphertext, 'hex')
+  const nonce = buf.subarray(0, NONCE_LENGTH)
+  const tag = buf.subarray(NONCE_LENGTH, NONCE_LENGTH + TAG_LENGTH)
+  const encrypted = buf.subarray(NONCE_LENGTH + TAG_LENGTH)
+  const decipher = crypto.createDecipheriv(ALGORITHM, key, nonce, { authTagLength: TAG_LENGTH })
+  decipher.setAuthTag(tag)
+  return decipher.update(encrypted) + decipher.final('utf8')
+}