fix: show progress bar instead of blank loading screen during bulk create

setLoading(true) was being called in onCreate, causing the component to
return <div>Loading...</div> early and hide the form and progress bar
entirely. Users saw a blank screen with no feedback until all requests
completed (or indefinitely for large counts like 50,000).

The loading state is only meant for edit mode (fetching an existing
subscriber's data). Batch creation progress is already tracked separately
via createProgress state, which drives the progress bar and button label.

Author: ALIIQBAL786

frontend/src/pages/SubscriberCreate/index.tsx

@@ -141,7 +141,9 @@ function SubscriberCreate() {
     const total = subscription.userNumber!;
     setCreateErrors([]);
     setCreateProgress({ current: 0, total });
-    setLoading(true);
+    // NOTE: do NOT set setLoading(true) here — loading is only for edit mode
+    // (fetching existing subscriber). Setting it here causes the component to
+    // return <div>Loading...</div> which hides the form and progress bar.
 
     // Build the full list of (supi, payload) pairs upfront so the loop body
     // is free of mutation side effects.
@@ -187,7 +189,6 @@ function SubscriberCreate() {
       setCreateProgress({ current: completed, total });
     }
 
-    setLoading(false);
     setCreateProgress(null);
 
     if (errors.length > 0) {