feat(plex): sort direction, genre any/all, multi-person filters; fix back-nav + player stop

UAT follow-ups on the Plex filter epic:
- Sort now has an asc/desc toggle (sort_dir), applied to any sort field.
- Genre multi-select gains an Any/All mode (genre_mode: OR vs AND containment).
- Director/actor/studio become multi-value: people AND (titles featuring all selected),
  studios OR; clicking them on the info page stacks (unions) instead of replacing, and
  the sidebar shows each as a removable 'Active' chip.
- fix(history): clicking a metadata filter on the info page now pushes a fresh grid
  entry instead of history.back(), so browser Back returns to the info page rather than
  leaving the Plex module.
- fix(player): fully tear down the <video> + hls on unmount and guard late play() calls,
  so backing out of a just-started video no longer leaves audio playing in the background.
i18n en/hu/de (match any/all, sort direction).

frontend/src/i18n/locales/de/plex.json

@@ -31,7 +31,9 @@
     "durationOpt": { "short": "Unter 90 Min.", "mid": "90–120 Min.", "long": "Über 2 Std." },
     "added": "Zu Plex hinzugefügt",
     "addedOpt": { "24h": "24 Std.", "1w": "1 Woche", "1m": "1 Monat", "6m": "6 Monate", "1y": "1 Jahr" },
-    "contentRating": "Altersfreigabe"
+    "contentRating": "Altersfreigabe",
+    "match": { "any": "Beliebig", "all": "Alle" },
+    "dir": { "desc": "↓ Absteigend", "asc": "↑ Aufsteigend" }
   },
   "count": "{{count}} Titel",
   "searchCount": "{{count}} Treffer",