fix: raise health report sender log level to INFO for observability

Changed "Sent health report" from DEBUG to INFO and failure log from
WARNING to ERROR so health report activity is visible in default logging.

src/ScadaLink.HealthMonitoring/HealthReportSender.cs

@@ -61,11 +61,11 @@ public class HealthReportSender : BackgroundService
 
                 _transport.Send(reportWithSeq);
 
-                _logger.LogDebug("Sent health report #{Seq} for site {SiteId}", seq, _siteId);
+                _logger.LogInformation("Sent health report #{Seq} for site {SiteId}", seq, _siteId);
             }
             catch (Exception ex)
             {
-                _logger.LogWarning(ex, "Failed to send health report for site {SiteId}", _siteId);
+                _logger.LogError(ex, "Failed to send health report for site {SiteId}", _siteId);
                 // Continue sending — don't let a single failure stop reporting
             }
         }