feat(audio,site): calm santoor default music + card-fan logo site redesign

- audio: default background music is now the santoor track (calm Persian),
  rebuilt as a real plucked-santoor loop — fast metallic attack, shimmer
  overtones, soft tonic drone, longer Dastgah-e-Shur phrase
- site: marketing logo is now the app's card-fan icon (Logo.tsx + icon.svg);
  hero features the big logo with gold halo, floating suit motifs, and
  polished section dividers

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

site/app/globals.css

@@ -78,3 +78,37 @@ body {
     linear-gradient(-45deg, rgba(212, 175, 55, 0.04) 25%, transparent 25%);
   background-size: 22px 22px;
 }
+
+/* Gentle float for the hero logo. */
+@keyframes float-y {
+  0%, 100% { transform: translateY(0); }
+  50% { transform: translateY(-12px); }
+}
+.float-y {
+  animation: float-y 5.5s ease-in-out infinite;
+}
+
+/* Soft gold halo behind the hero logo. */
+.gold-halo {
+  background: radial-gradient(circle, rgba(212, 175, 55, 0.28), transparent 62%);
+  filter: blur(8px);
+}
+
+/* Card-suit accent for hero/section glyphs. */
+.suit {
+  color: var(--gold);
+  opacity: 0.16;
+  user-select: none;
+  line-height: 1;
+}
+
+/* Thin gold hairline divider. */
+.rule-gold {
+  height: 1px;
+  background: linear-gradient(90deg, transparent, rgba(212, 175, 55, 0.5), transparent);
+}
+
+@media (prefers-reduced-motion: reduce) {
+  .float-y { animation: none; }
+  html { scroll-behavior: auto; }
+}