fix: chat::save_msgs: Interrupt inbox loop to send a sync message

Also fix the `send_sync_msg()` documentation: now it's called from the inbox loop, not SMTP (because
`IMAP APPEND` is used to upload sync messages).

src/chat.rs

@@ -4374,7 +4374,7 @@ pub async fn save_msgs(context: &Context, msg_ids: &[MsgId]) -> Result<()> {
             })
             .await?;
     }
-    context.send_sync_msg().await?;
+    context.scheduler.interrupt_inbox().await;
     Ok(())
 }
 

src/sync.rs

@@ -169,7 +169,7 @@ impl Context {
     ///
     /// Mustn't be called from multiple tasks in parallel to avoid sending the same sync items twice
     /// because sync items are removed from the db only after successful sending. We guarantee this
-    /// by calling `send_sync_msg()` only from the SMTP loop.
+    /// by calling `send_sync_msg()` only from the inbox loop.
     pub async fn send_sync_msg(&self) -> Result<Option<MsgId>> {
         if let Some((json, ids)) = self.build_sync_json().await? {
             let chat_id =