feat: add Pro feature paywall and unlock overlay UI.

frontend/components/subscription/UnlockProOverlay.module.css

@@ -6,6 +6,9 @@
   max-height: calc(100dvh - 2.5rem);
   overflow-x: hidden;
   overflow-y: auto;
+  /* Hide scrollbar — all browsers */
+  scrollbar-width: none; /* Firefox */
+  -ms-overflow-style: none; /* IE / Edge legacy */
   border-radius: 28px;
   border: 1px solid rgba(255, 255, 255, 0.07);
   background: linear-gradient(160deg, #111827 0%, #0d1525 40%, #090f1c 100%);
@@ -16,6 +19,11 @@
   padding: 28px 24px 24px;
 }
 
+/* Chrome / Safari / WebKit */
+.modal::-webkit-scrollbar {
+  display: none;
+}
+
 @media (min-width: 768px) {
   .modal {
     padding: 36px 36px 28px;