♻️(frontend) extract layout constants for alignment

Move hardcoded values used for layout alignment and animations
between the videoconference and side panel into shared constants.

This improves readability and makes future adjustments easier to
maintain.

src/frontend/panda.config.ts

@@ -274,6 +274,10 @@ const config: Config = {
         min: { value: 'min-content' },
         max: { value: 'max-content' },
         fit: { value: 'fit-content' },
+        // room layout
+        'room-side-panel': { value: '360px' },
+        'room-side-panel-margin': { value: '1.5rem' },
+        'room-control-bar': { value: '80px' },
       },
       spacing,
     }),