fix(backend): restore streak hourOffset migration guard

Author: chinmaydwivedi

backend/src/dal/user.ts

@@ -1146,6 +1146,11 @@ export async function updateStreak(
 
   streak.lastResultTimestamp = timestamp;
 
+  if (user.streak?.hourOffset === 0) {
+    // todo this needs to be removed after a while
+    delete streak.hourOffset;
+  }
+
   await getUsersCollection().updateOne({ uid }, { $set: { streak } });
 
   return streak.length;