Make dashboard sidebar scrollable

docs/frontend.md

@@ -87,6 +87,7 @@ Keep feature components focused:
 ## Accessibility and presentation
 
 - All actions must be keyboard accessible and have visible focus.
+- The fixed primary sidebar is its own vertical scroll region so every route and the platform controls remain reachable on short or low-resolution screens.
 - Dialogs label purpose, trap/restore focus, and distinguish cancel from destructive confirmation.
 - Status must not rely on color alone.
 - Relative times include an exact timestamp where operationally useful.