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>

server/routes/adminNostr.ts

@@ -0,0 +1,26 @@
+import { Router } from 'express'
+import { adminAuth } from '../middleware/adminAuth.js'
+
+export const adminNostrRouter = Router()
+adminNostrRouter.use(adminAuth)
+
+adminNostrRouter.get('/nostr-info', async (_req, res) => {
+  const privkeyHex = process.env.NOSTR_PRIVATE_KEY
+  if (!privkeyHex) {
+    res.status(404).json({ error: { code: 'NOT_CONFIGURED', message: 'NOSTR_PRIVATE_KEY not set' } })
+    return
+  }
+
+  try {
+    const { getPublicKey } = await import('nostr-tools/pure')
+    const { npubEncode } = await import('nostr-tools/nip19')
+    const privkey = Uint8Array.from(Buffer.from(privkeyHex, 'hex'))
+    const pubkey = getPublicKey(privkey)
+    const npub = npubEncode(pubkey)
+    privkey.fill(0)
+
+    res.json({ npub, pubkey })
+  } catch {
+    res.status(500).json({ error: { code: 'NOSTR_ERROR', message: 'Failed to derive public key' } })
+  }
+})