Add pricing entry flow and platform admin foundations

lib/core/services/realtime_service.dart

@@ -16,21 +16,33 @@ class RealtimeService {
     required void Function(RecordSubscriptionEvent) onEvent,
   }) {
     UnsubFn? cancel;
+    bool disposeRequested = false;
+    bool disposed = false;
 
-    _pb.collection(collection).subscribe(topic, onEvent, filter: filter).then((fn) {
+    _pb
+        .collection(collection)
+        .subscribe(topic, onEvent, filter: filter)
+        .then((fn) async {
+      if (disposeRequested) {
+        disposed = true;
+        await fn();
+        return;
+      }
       cancel = fn;
-    });
+    }).catchError((_) {});
 
     return () async {
+      if (disposed) return;
+      disposeRequested = true;
       try {
         final fn = cancel;
         if (fn != null) {
+          disposed = true;
           await fn();
-        } else {
-          await _pb.collection(collection).unsubscribe(topic);
         }
       } catch (_) {
-        await _pb.collection(collection).unsubscribe(topic);
+        // swallow — never globally unsubscribe the topic here, because
+        // other screens may still be subscribed to the same collection/topic.
       }
     };
   }