fix(e5): Plex detail/UI polish from review (backdrop reset, layout, combobox, labels)

User-reported issues after the E5 build:

- useCrossfadeBackdrop: the static branch (one image / crossfade off /
  reduced motion) painted #root but returned NO cleanup, so the backdrop
  persisted after leaving the page (e.g. switching modules). Every painted
  branch now returns clear() so unmount always resets the default backdrop.
- scheduler: give the tmdb_enrich job a proper label + description (was the
  raw "tmdb_enrich" id) in EN/HU.
- CastStrip: cap crew names to ONE line (truncate) so the row of circular
  photos sits on one baseline instead of going wavy on 2-line names.
- PlexInfo: lay Details / Keywords / Crew out as side-by-side boxes
  (items-start grid) instead of full-width stacked panels with dead space;
  narrower Crew grid for the boxed width; each panel independently hideable
  from the customize menu (new Details/Keywords/Crew toggles). Tighter
  vertical spacing.
- MultiSelectChips: reshape the trigger from a "+Add" button into an
  Overseerr-style combi input — removable chips inside a typeable field that
  filters the checklist, opening on focus (backspace removes the last chip).
- Discover / person rails: reduce the vertical gap between rails.

frontend/src/components/plexCards.tsx

@@ -348,12 +348,19 @@ export function CastStrip({
                   </div>
                 )}
               </div>
+              {/* Name + role are each capped to ONE line (truncate → ellipsis) so every tile has the
+                  same text height and the row of circles sits on one baseline regardless of name length. */}
               <div
-                className={`mt-1.5 text-xs font-medium line-clamp-2 leading-tight ${clickable ? "group-hover/cast:text-accent" : ""}`}
+                className={`mt-1.5 truncate text-xs font-medium leading-tight ${clickable ? "group-hover/cast:text-accent" : ""}`}
+                title={c.name}
               >
                 {c.name}
               </div>
-              {c.role && <div className="text-2xs text-muted line-clamp-1">{c.role}</div>}
+              {c.role && (
+                <div className="truncate text-2xs text-muted" title={c.role}>
+                  {c.role}
+                </div>
+              )}
             </>
           );
           return clickable ? (