fix: setError(null) was overriding setProcessing(true)

The Zustand setError() setter has a side effect: it sets
processing=false. When called after setProcessing(true), it
immediately killed the processing state, so the ProgressCard
never rendered. Fix: call setError(null) before setProcessing(true).

apps/web/src/hooks/use-tool-processor.ts

@@ -68,9 +68,9 @@ export function useToolProcessor(toolId: string) {
         return;
       }
 
-      setProcessing(true);
       setError(null);
       setProcessedUrl(null);
+      setProcessing(true);
       setProgress({ phase: "uploading", percent: 0, elapsed: 0 });
 
       // Start elapsed timer