Fix unsubscribe + reduce bot update db query

src/Managing.Application/Grains/CandleStoreGrain.cs

@@ -67,11 +67,25 @@ public class CandleStoreGrain : Grain, ICandleStoreGrain, IAsyncObserver<Candle>
 
     public override async Task OnDeactivateAsync(DeactivationReason reason, CancellationToken cancellationToken)
     {
-        // Unsubscribe from the stream
+        // Unsubscribe from the stream with proper error handling
         if (_streamSubscription != null)
         {
-            await _streamSubscription.UnsubscribeAsync();
-            _streamSubscription = null;
+            try
+            {
+                await _streamSubscription.UnsubscribeAsync();
+                _logger.LogDebug("Successfully unsubscribed from stream for grain {GrainKey}", this.GetPrimaryKeyString());
+            }
+            catch (Exception ex)
+            {
+                // Log the error but don't throw - this is common during shutdown when
+                // the pub-sub rendezvous grain may already be deactivated
+                _logger.LogWarning(ex, "Failed to unsubscribe from stream during deactivation for grain {GrainKey}. This is normal during shutdown.", 
+                    this.GetPrimaryKeyString());
+            }
+            finally
+            {
+                _streamSubscription = null;
+            }
         }
 
         await base.OnDeactivateAsync(reason, cancellationToken);