Production-ready overhaul: backend fixes, claim flow polish, SEO, mobile, nginx

Backend:
- Fix activity score (followersCount check), NIP-98 URL proto, wallet balance guard
- Add payment_hash to confirm response, spentTodaySats to stats
- Add idx_claims_ip_hash; security headers, graceful shutdown, periodic nonce cleanup

Frontend:
- Remove 8 legacy components; polish wizard (rules summary, profile card, confetti, share)
- Stats budget bar uses spentTodaySats; ErrorBoundary with reload

SEO & production:
- Full meta/OG/Twitter, favicon, JSON-LD, robots.txt, sitemap.xml
- Mobile CSS fixes; nginx static dist + gzip + cache + security headers
- Vite manualChunks; aria-labels, dynamic page titles

Made-with: Cursor

backend/src/db/schema.sql

@@ -64,6 +64,7 @@ CREATE TABLE IF NOT EXISTS deposits (
 
 CREATE INDEX IF NOT EXISTS idx_claims_pubkey ON claims(pubkey);
 CREATE INDEX IF NOT EXISTS idx_claims_claimed_at ON claims(claimed_at);
+CREATE INDEX IF NOT EXISTS idx_claims_ip_hash ON claims(ip_hash);
 CREATE INDEX IF NOT EXISTS idx_quotes_expires_at ON quotes(expires_at);
 CREATE INDEX IF NOT EXISTS idx_quotes_status ON quotes(status);
 CREATE INDEX IF NOT EXISTS idx_deposits_created_at ON deposits(created_at);