Fix job DAG edges rendering above nodes

Replace glass-card (backdrop-filter) on operator nodes with a solid
background and explicit z-index. backdrop-filter creates a new stacking
context that breaks paint order, causing edge arrows to appear on top
of nodes. Also removes the backpressure left-border indicator.

Author: sandboxws

dashboard/src/components/jobs/detail/operator-node.tsx

@@ -196,10 +196,7 @@ export function OperatorNode({ data }: NodeProps & { data: OperatorNodeData }) {
   const nodeContent = (
     <div
       title=""
-      className={cn(
-        "glass-card w-[320px] border-l-[3px] overflow-hidden",
-        bpColor(metrics.busyTimeMsPerSecond),
-      )}
+      className="relative z-10 w-[320px] overflow-hidden rounded-xl border border-white/6 bg-dash-panel"
     >
       <Handle
         type="target"