feat: placeholder images, Nostr inbox, order lookup, SEO, bigger logo

- 5 SVG placeholder product images (minimal dark style with watermark initials)
- Seed data updated to reference .svg placeholders
- Nostr DM inbox in admin (Messages tab) with shop npub display
- GET /api/admin/nostr-info endpoint for shop pubkey
- My Orders page: customers look up orders by NIP-07 Nostr identity
- GET /api/orders/by-pubkey/:pubkey endpoint with hex validation
- SeoMeta component for OG/Twitter meta tags
- SEO meta on HomeView and ProductView
- Base OG meta tags in index.html
- "My Orders" link in shop header nav
- Splash logo doubled in size on desktop (680px max)

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

index.html

@@ -5,6 +5,12 @@
     <link rel="icon" type="image/svg+xml" href="/logos/logo.svg" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>Antonym</title>
+    <meta name="description" content="Fashion for the sovereign individual. Bitcoin only. No accounts. No tracking." />
+    <meta property="og:title" content="Antonym" />
+    <meta property="og:description" content="Fashion for the sovereign individual. Bitcoin only. No accounts. No tracking." />
+    <meta property="og:image" content="/logos/logo.svg" />
+    <meta property="og:type" content="website" />
+    <meta name="twitter:card" content="summary_large_image" />
     <link rel="preconnect" href="https://fonts.googleapis.com" />
     <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />
     <link href="https://fonts.googleapis.com/css2?family=Bebas+Neue&family=Playfair+Display:ital,wght@1,900&display=swap" rel="stylesheet" />