fix: elevate share nostr modal z-index

Ensure the Share on Nostr modal renders above the video player modal by applying the higher z-index tier variables (z-modal-top-root, etc.), similar to the Profile modal.

Fixes an issue where the share modal was obscured by the video player.

css/tailwind.source.css

@@ -3727,6 +3727,18 @@
     z-index: var(--z-modal-top-content);
   }
 
+  #modalContainer > #shareNostrModal {
+    z-index: var(--z-modal-top-root);
+  }
+
+  #modalContainer > #shareNostrModal > .bv-modal-backdrop {
+    z-index: var(--z-modal-top-overlay);
+  }
+
+  #modalContainer > #shareNostrModal .bv-modal__panel {
+    z-index: var(--z-modal-top-content);
+  }
+
   .bv-modal[data-nested-modal-active="true"] {
     pointer-events: none;
     visibility: hidden;