feat(ui): offer programme details from the live channel context menu

The Xtream and Stalker live sidebars hide the per-row (i) button by
design — the current programme is already inline — which left no way to
read a programme description without switching channels. Right-click now
offers "Show program details" (opening the existing EPG description
dialog) in both portal sidebars and in the favorites/recently-viewed
lists, whenever the row has a current programme. The context menu is no
longer gated on EPG-mapping support alone, so the item also works in the
PWA.

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

.changes/ui-program-details-context-menu.md

@@ -0,0 +1,9 @@
+---
+type: feature
+area: ui
+---
+
+Right-clicking a live channel now offers "Show program details" in the
+context menu — in the Xtream and Stalker channel sidebars and in the
+favorites and recently-viewed lists — whenever the channel has current
+programme information.