feat: 캔 엔티티 currency - length 3으로 고정하여 CHAR(3)에 대응되도록 수정

src/main/kotlin/kr/co/vividnext/sodalive/can/Can.kt

@@ -14,7 +14,7 @@ data class Can(
     var rewardCan: Int,
     @Column(precision = 10, scale = 4, nullable = false)
     var price: BigDecimal,
-    @Column(length = 3, nullable = false)
+    @Column(length = 3, nullable = false, columnDefinition = "CHAR(3)")
     var currency: String,
     @Enumerated(value = EnumType.STRING)
     var status: CanStatus