feat(ui): add a desktop panel rail to each sidebar

Each side stack hosts a Vue rail listing its panels; selecting one opens it
through PanelChrome. The shell owns one Vue runtime and Pinia instance, and a
panel store mirrors each side's panels from the DOM. The rail hides with its
stack, in Cockpit, clean view and recording, and on phones. Panels without a
catalog entry get a generic item, and Data Layers leaves the rail while the
f shortcut hides it.

src/i18n/locales/de.json

@@ -2943,5 +2943,7 @@
   "Load scenes from an exported JSON file": "Szenen aus einer exportierten JSON-Datei laden",
   "Download the timing log of the last play": "Zeitprotokoll der letzten Wiedergabe herunterladen",
   "Edit anchors, data packs and shot details": "Anker, Datenpakete und Aufnahmedetails bearbeiten",
-  "Download this scene as JSON or an asset bundle": "Diese Szene als JSON oder Asset-Bundle herunterladen"
+  "Download this scene as JSON or an asset bundle": "Diese Szene als JSON oder Asset-Bundle herunterladen",
+  "Left panels": "Linke Panels",
+  "Right panels": "Rechte Panels"
 }