Fix session replica behaviour (merge with session)

The harder-to-refactor parts are the places where exists/username/token
are called within a React component. However, `resetAndRedirect` and
`store` are already called from async contexts, so adding an `await`
is simple.

This thus merges the logic, keeping localStorage for the components to
call, but making sure reset/store behaviour works correctly for the
replica.

web/src/components/ActionBar.jsx

@@ -123,7 +123,7 @@ const ProfileIcon = () => {
       await accountApi.logout();
       await db().delete();
     } finally {
-      session.resetAndRedirect(routes.app);
+      await session.resetAndRedirect(routes.app);
     }
   };