feat(portal): mark movies as watched from the detail page (#1605)

.changes/portal-mark-movie-watched.md

@@ -0,0 +1,10 @@
+---
+type: feature
+area: portal
+---
+
+Movies can now be marked as watched (or unwatched) by hand from their
+detail page on Xtream and Stalker sources, including the Favorites and
+Recently Viewed views — the same way seasons and episodes already could. The
+catalog shows the green check right away, and a watched movie offers Play
+instead of a Resume near the end.