refactor: simplify buffered location retry logic

- Remove immediate flush trigger on network change
- Buffered locations now retry on every location send and heartbeat
- Heartbeat interval already covers retry needs, no need for extra trigger

android/app/src/main/kotlin/dev/fiatcode/tracpulse/service/LocationTrackingService.kt

@@ -79,7 +79,6 @@ class LocationTrackingService : Service() {
         connectivityReceiver = ConnectivityReceiver { online ->
             isNetworkAvailable = online
             logEvent("NETWORK_CHANGE", "Network: ${if (online) "online" else "offline"}")
-            if (online) syncBufferedLocations()
         }
 
         val intentFilter = IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION)
@@ -389,6 +388,8 @@ class LocationTrackingService : Service() {
                 logEvent("ERROR", "Failed to send location: ${result.exceptionOrNull()?.message}")
                 bufferLocation(location)
             }
+            // Also try to flush any buffered locations after each send attempt
+            syncBufferedLocations()
         }
     }