Remove auto-sync timers, keep only manual sync

Sync engine no longer has push (30s) or pull (5min) intervals.
Sync only happens on launch (InitialSync), manual Ctrl+R (FullSync),
or after create/edit/delete (TriggerSync).

src/main.rs

@@ -164,20 +164,8 @@ async fn run_sync_engine(
     sync_stats: Arc<Mutex<SyncStats>>,
     rx: &mut tokio::sync::mpsc::Receiver<SyncCommand>,
 ) {
-    let mut push_interval = tokio::time::interval(tokio::time::Duration::from_secs(30));
-    let mut pull_interval = tokio::time::interval(tokio::time::Duration::from_secs(300));
-    pull_interval.tick().await;
-
     loop {
-        tokio::select! {
-            _ = push_interval.tick() => {
-                push_sync(&db, &api, &network_status, &sync_stats).await;
-            }
-            _ = pull_interval.tick() => {
-                pull_sync(&db, &api, &network_status, &sync_stats, false).await;
-            }
-            cmd = rx.recv() => {
-                match cmd {
+        match rx.recv().await {
             Some(SyncCommand::TriggerSync) => {
                 push_sync(&db, &api, &network_status, &sync_stats).await;
             }
@@ -191,8 +179,6 @@ async fn run_sync_engine(
             Some(SyncCommand::Shutdown) | None => break,
         }
     }
-        }
-    }
 }
 
 async fn run_initial_sync(