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>

src/components/ui/LoadingSpinner.vue

@@ -0,0 +1,30 @@
+<script setup lang="ts">
+</script>
+
+<template>
+  <div class="spinner-container">
+    <div class="spinner" />
+  </div>
+</template>
+
+<style scoped>
+.spinner-container {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  padding: 2rem;
+}
+
+.spinner {
+  width: 32px;
+  height: 32px;
+  border: 2px solid var(--glass-border);
+  border-top-color: var(--accent);
+  border-radius: 50%;
+  animation: spin 0.8s linear infinite;
+}
+
+@keyframes spin {
+  to { transform: rotate(360deg); }
+}
+</style>