feat: Nostr profile enrichment with caching

Fetch full kind:0 metadata (display_name, about, banner, nip05) from
relays with a 5-min TTL cache. Show Nostr banner, display name, and
NIP-05 on bot profile pages. Expose ownerPubkey in stats API.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/routes/bots.ts

@@ -268,6 +268,7 @@ botsRouter.get('/:name/stats', async (c) => {
 
   return c.json({
     ...publicBot,
+    ownerPubkey: rawBot.publicKey,
     tierName: TIER_NAMES[bot.tier] || 'BABY',
     tierColor: TIER_COLORS[bot.tier] || '#888',
     winRate,