feat: complete header and dropdown redesign for professional look

- Redesign site header with multi-layer gradient overlays, decorative glows, dot pattern texture, responsive clamp font sizing, and animated ping online badge
- Add glass-dropdown CSS class with 60% opacity backdrop blur (20px) and smooth dropdownIn animation (scale + translate)
- Fix dropdown positioning with top-full for proper alignment under menu triggers
- Standardize all dropdowns (nav, top-header, color picker, language switcher) to use glass-dropdown class

src/app/globals.css

@@ -900,12 +900,28 @@ tbody tr:hover {
   border-color: #f97316;
 }
 
-/* ── Glass dropdown (backdrop blur) ─────────────────────────── */
+/* ── Glass dropdown (backdrop blur + animation) ─────────────── */
 .glass-dropdown {
-  backdrop-filter: blur(16px) saturate(180%);
-  -webkit-backdrop-filter: blur(16px) saturate(180%);
-  background-color: color-mix(in srgb, var(--color-dropdown) 78%, transparent);
-  border: 1px solid color-mix(in srgb, var(--color-text-muted) 12%, transparent);
+  backdrop-filter: blur(20px) saturate(200%);
+  -webkit-backdrop-filter: blur(20px) saturate(200%);
+  background-color: color-mix(in srgb, var(--color-dropdown) 60%, transparent);
+  border: 1px solid color-mix(in srgb, var(--color-text-muted) 14%, transparent);
+  box-shadow: 0 8px 32px color-mix(in srgb, rgb(0 0 0) 20%, transparent);
+}
+
+details[open] > .glass-dropdown {
+  animation: dropdownIn 0.15s ease-out;
+}
+
+@keyframes dropdownIn {
+  from {
+    opacity: 0;
+    transform: translateY(-6px) scale(0.97);
+  }
+  to {
+    opacity: 1;
+    transform: translateY(0) scale(1);
+  }
 }
 
 /* ── Radio sidebar ──────────────────────────────────────────── */