ui: realm: clarify that the sync jobs really are for the realm

ui: realm: clarify that the sync jobs really are for the realm

it's somewhat redundant as onbe is already at the realm view, but for
panel titles it slightly helps if one doesn't have to string together
such "clues" oneself, i.e., it's easier to see where one is - e.g.,
if switching from some other task back to the web UI again, and we
have enough space here, so we ain't winning anything if keeping it
short.

Also add an emptyText to the grid, mostly as view's without anything
always look a bit off (like an error happened on load and one forgot
to mask)

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>