feat(player): open YouTube's native settings menu fully + push higher quality

The transparent interaction overlay (click=play/pause, wheel=volume, keeps
keyboard focus off the cross-origin iframe) also blocked YouTube's own settings
menu, which expands down over the video past the overlay: items below the first
few were unclickable, and 'More options' made it worse.

Now the overlay yields to native controls. Clicking a native control (gear/seek/
CC) moves focus into the player iframe — the only cross-origin signal available —
which we detect (window blur + getIframe() focus check) to drop the overlay's
pointer-events, so the whole menu is navigable at any height. A discreet badge
signals native mode; moving the pointer off the video (or the window regaining
focus) re-arms the click/scroll/keyboard shortcuts.

Quality: the IFrame API's setPlaybackQuality/suggestedQuality are hard no-ops now,
so the real lever is the rendered player size — bump the modal max-w-4xl -> 6xl so
YouTube's ABR targets a higher resolution — plus a best-effort 'vq=hd1080' URL hint.
i18n (en/hu/de) for the native-mode badge.

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

@@ -35,5 +35,6 @@
   "unavailableBody": "Dieses Video ist nicht verfügbar — möglicherweise privat, entfernt oder regional gesperrt.",
   "embedDisabledBody": "Der Eigentümer hat die Wiedergabe auf anderen Seiten deaktiviert (häufig bei automatisch generierten „Topic“-Musiktiteln). Auf YouTube ist es weiterhin abspielbar.",
   "openOnYoutube": "Auf YouTube öffnen",
-  "shortcutsHint": "Klick: Wiedergabe/Pause · Scrollen: Lautstärke · F: Vollbild"
+  "shortcutsHint": "Klick: Wiedergabe/Pause · Scrollen: Lautstärke · F: Vollbild",
+  "nativeControls": "YouTube-Steuerung aktiv"
 }