[Bug] not handle negative values when process the accuracy range of datetime

### Search before asking

- [x] I had searched in the [issues](https://github.com/apache/incubator-doris/issues?q=is%3Aissue) and found no similar issues.

### Version

Apache Doris: 2.1.6
Flink: 1.20
flink-doris-connector: 1.20-25.1.0-SNAPSHOT

### What's Wrong?

When using Flink to read Doris' datetime type field, if the long value of the datetime is negative, an exception will occur because accuracy has not been processed.
Expection:`java.time.DateTimeException: Instant exceeds minimum or maximum instant`

### What You Expected?

Properly handle datetime accuracy

### How to Reproduce?

_No response_

### Anything Else?

_No response_

### Are you willing to submit PR?

- [x] Yes I am willing to submit a PR!

### Code of Conduct

- [x] I agree to follow this project's [Code of Conduct](https://www.apache.org/foundation/policies/conduct)

Start by locating the Java code that processes datetime accuracy when reading Doris datetime fields through the Flink connector. Reproduce the failure with a negative long datetime value if possible, then verify that negative values are handled without the reported DateTimeException. The issue provides no test or file path, so the relevant entry point must be found first.

Written by the indexing model from the issue text.