Add room-stay void/checkout controls and audit logs

src/main/kotlin/com/android/trisolarisserver/models/room/RoomStay.kt

@@ -33,6 +33,9 @@ class RoomStay(
     @Column(name = "to_at", columnDefinition = "timestamptz")
     var toAt: OffsetDateTime? = null,   // null = active
 
+    @Column(name = "is_voided", nullable = false)
+    var isVoided: Boolean = false,
+
     @Enumerated(EnumType.STRING)
     @Column(name = "rate_source")
     var rateSource: RateSource? = null,