Fix: timezone-related test failures in JsonNormalizerTest (#83) (#84)

* Replace hardcoded timezone values with dynamic computation based on system timezone
* Update testSQLTime to use time.toLocalTime().format(DateTimeFormatter.ISO_LOCAL_TIME)
* Update testSQLTimeStamp to use dateTime.toLocalDateTime().format(DateTimeFormatter.ISO_LOCAL_DATE_TIME)
* Update Calendar and GregorianCalendar tests to use input.toInstant().toString()
* Add missing DateTimeFormatter import for time formatting

Author: nileader

src/test/java/dev/toonformat/jtoon/normalizer/JsonNormalizerTest.java

@@ -30,6 +30,7 @@
 import java.time.ZoneId;
 import java.time.ZoneOffset;
 import java.time.ZonedDateTime;
+import java.time.format.DateTimeFormatter;
 import java.util.Calendar;
 import java.util.Collection;
 import java.util.Date;
@@ -345,7 +346,8 @@ void testSQLTime() {
             java.sql.Time time = new java.sql.Time(1766419274);
             JsonNode result = JsonNormalizer.normalize(time);
             assertTrue(result.isString());
-            assertEquals("11:40:19", result.asString());
+            String expected = time.toLocalTime().format(DateTimeFormatter.ISO_LOCAL_TIME);
+            assertEquals(expected, result.asString());
         }
 
         @Test
@@ -354,7 +356,8 @@ void testSQLTimeStamp() {
             java.sql.Timestamp dateTime = new java.sql.Timestamp(1766419274);
             JsonNode result = JsonNormalizer.normalize(dateTime);
             assertTrue(result.isString());
-            assertEquals("1970-01-21T11:40:19.274", result.asString());
+            String expected = dateTime.toLocalDateTime().format(DateTimeFormatter.ISO_LOCAL_DATE_TIME);
+            assertEquals(expected, result.asString());
         }
 
 
@@ -1191,7 +1194,8 @@ void givenCalendar_whenTryNormalizeTemporal_thenIsoStringNode() throws Exception
 
             // Then
             assertInstanceOf(StringNode.class, result);
-            assertEquals("2017-02-16T19:22:28Z", ((JsonNode) result).asString());
+            String expected = input.toInstant().toString();
+            assertEquals(expected, ((JsonNode) result).asString());
         }
 
         @Test
@@ -1205,7 +1209,8 @@ void givenGregorianCalendar_whenTryNormalizeTemporal_thenIsoStringNode() throws
 
             // Then
             assertInstanceOf(StringNode.class, result);
-            assertEquals("2017-02-16T19:22:28Z", ((JsonNode) result).asString());
+            String expected = input.toInstant().toString();
+            assertEquals(expected, ((JsonNode) result).asString());
         }
 
         @Test