fix(quick-17): add visible empty state styling for fullBleed nodes

- Change fullBleed nodes from transparent to subtle bg-neutral-800/50 with border-neutral-700/40
- Makes empty GenerateImage, GenerateVideo, and LLMGenerate nodes visible on canvas
- Content still covers background when present (images/videos fill the area)

src/components/nodes/BaseNode.tsx

@@ -76,7 +76,7 @@ export function BaseNode({
       <div
         className={`
           h-full w-full flex flex-col overflow-visible
-          ${fullBleed ? "rounded-lg" : "bg-neutral-800 rounded-lg shadow-lg border"}
+          ${fullBleed ? "rounded-lg bg-neutral-800/50 border border-neutral-700/40" : "bg-neutral-800 rounded-lg shadow-lg border"}
           ${fullBleed ? "" : (isCurrentlyExecuting || isExecuting ? "border-blue-500 ring-1 ring-blue-500/20" : "border-neutral-700/60")}
           ${fullBleed ? "" : (hasError ? "border-red-500" : "")}
           ${fullBleed && selected ? "ring-2 ring-blue-500/40 shadow-lg shadow-blue-500/25" : ""}