Fix: Enable video modal share button when source is available

The share button in the video modal was not being enabled correctly because `updateSourceAvailability` returned early if `sourceToggleContainer` was missing, skipping the `setShareEnabled` call.

This change ensures `setShareEnabled` is called based on `hasUrl` or `hasMagnet` before checking for `sourceToggleContainer`.

Added a regression test `tests/e2e/video-modal-share-bug.spec.ts`.

js/ui/components/VideoModal.js

@@ -2797,10 +2797,6 @@ export class VideoModal {
   }
 
   updateSourceAvailability(video) {
-    if (!this.sourceToggleContainer) {
-      return;
-    }
-
     const hasUrl = Boolean(
       typeof video?.url === "string" && video.url.trim()
     );
@@ -2809,6 +2805,12 @@ export class VideoModal {
         video?.torrentSupported
     );
 
+    this.setShareEnabled(hasUrl || hasMagnet);
+
+    if (!this.sourceToggleContainer) {
+      return;
+    }
+
     if (hasUrl || hasMagnet) {
       this.sourceToggleContainer.removeAttribute("hidden");
       this.sourceToggleContainer.classList.remove("hidden");