fix: snapshot existing config before update; rollback returns 200

k-tv-backend/api/src/routes/channels/schedule.rs

@@ -130,5 +130,5 @@ pub(super) async fn rollback_schedule(
     let detail = format!("rollback to gen {}; {} slots", target.generation, schedule.slots.len());
     let _ = state.activity_log_repo.log("schedule_rollback", &detail, Some(channel_id)).await;
 
-    Ok((StatusCode::CREATED, Json(ScheduleResponse::from(schedule))))
+    Ok(Json(ScheduleResponse::from(schedule)))
 }

k-tv-backend/domain/src/services/channel.rs

@@ -44,10 +44,12 @@ impl ChannelService {
     }
 
     pub async fn update(&self, channel: Channel) -> DomainResult<Channel> {
-        // Auto-snapshot the config being replaced
-        self.channel_repo
-            .save_config_snapshot(channel.id, &channel.schedule_config, None)
-            .await?;
+        // Auto-snapshot the existing config before overwriting
+        if let Some(existing) = self.channel_repo.find_by_id(channel.id).await? {
+            self.channel_repo
+                .save_config_snapshot(channel.id, &existing.schedule_config, None)
+                .await?;
+        }
         self.channel_repo.save(&channel).await?;
         Ok(channel)
     }