feat: streamline traefik widget with icon/status dot, fix grid gap

Traefik's widget was the only card without a BrandIcon or StatusDot in
its header, and had no href either - added icon/href fields to the
schema and matched the exact docker/service widget header markup.
StatusDot reuses the same "running once data loaded" convention the
other widgets already use for a non-container up/down signal.

System's widget was span=5 while every other widget in this app is
span=4 (docker/service/traefik) or 3 (http) - on a 12-column grid that
left a permanent 3-column gap next to it every row. Matched it to
span=4 so system+traefik+one more widget tile a full row exactly.
Also added grid-auto-flow: dense as a general safety net against
future span-mismatch gaps.

app/globals.css

@@ -144,6 +144,7 @@ body {
 .pn-bento {
   display: grid;
   grid-template-columns: repeat(12, 1fr);
+  grid-auto-flow: dense;
 }
 
 @media (max-width: 860px) {