feat: add java.sql.Date converters (#1017) - #1289

Purpose of the pull request

Related: #1017 (java.sql.Date slice). Proposal: #1017 (comment)

java.sql.Date is the last java.sql type without converters. Converters are keyed by the exact class, so a java.sql.Date field fails on read and write with Can not find 'Converter' support class Date, even though java.util.Date is supported. This mirrors java.sql.Time (#1092) and java.sql.Timestamp (#1220).

What's changed?

Added converters/sqldate and registered it in DefaultConverterLoader:

• SqlDateNumberConverter (Excel NUMBER): reads through DateUtils.getLocalDate(serial, use1904windowing) → Date.valueOf(LocalDate), returning null for invalid serials; writes DateUtil.getExcelDate(value.toLocalDate(), use1904windowing).
• SqlDateStringConverter (Excel STRING): parses/formats through LocalDate, honoring @DateTimeFormat and GlobalConfiguration.locale.
• SqlDateDateConverter (write only, DATE cell): uses DateUtils.defaultLocalDateFormat unless @DateTimeFormat overrides it.

Registration matches the java.sql.Time / java.sql.Timestamp pattern; no existing behavior changes.

Verification

• Red side (registrations removed): the XLSX/XLS/CSV round trip fails on all three formats with ExcelWriteDataConvertException: Can not find 'Converter' support class Date, and the loader registration test fails.
• Green side: SqlDateConverterTest 10/10 and SqlDateRoundTripTest 3/3 (XLSX, XLS, CSV).
• Full build mvn clean package -B -Dmaven.test.skip=false -pl fesod-common,fesod-shaded,fesod-sheet: 1,862 tests, 0 failures.
• spotless:check and javadoc:javadoc pass.

Checklist

• I have read the Contributor Guide.
• I have written the necessary doc or comment.
• I have added the necessary unit tests and all cases have passed.