fix: remove redundant 4-hour temperature fallback log to reduce noise

app/Jobs/Machine/ProcessHeartbeat.php

@@ -99,10 +99,6 @@ class ProcessHeartbeat implements ShouldQueue
                     Log::debug("ProcessHeartbeat: Temperature changed from {$lastValue} to {$temp}. Triggering log.");
                     $shouldLog = true;
                 }
-                // 條件 B: 距離上次日誌超過 4 小時 (保底機制)
-                if ($lastAt->diffInHours(now()) >= 4) {
-                    $shouldLog = true;
-                }
             }
 
             if ($shouldLog) {