fix(portals): re-run TMDB season enrichment when the show match arrives

With season tabs the first seasonSelected fires as soon as seasons
load — usually before the async show-level TMDB enrichment has written
tmdb_id — so the season fetch silently no-oped and was never retried,
leaving episode stills/plots and the season description empty. Both
detail hosts now key the fetch on (tmdb_id, selected season) in an
effect, so it runs whichever arrives last. Also adds breathing room
above the About divider in watch state.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

libs/ui/components/src/lib/portal-detail-shell/portal-detail-shell.component.scss

@@ -90,6 +90,9 @@
 }
 
 .shell__about {
+    display: block;
+    // Air between the last episode row and the section divider.
+    margin-top: 32px;
     animation: shell-fade-in 250ms ease 100ms both;
 }