Extract SqliteDateTimeValues from LibsqlResultSet #201

Goal

Move SQLite storage-class to date and time conversion out of LibsqlResultSet. It is about 112 lines of Julian-day math, SQLite text formats, offsets, and target-type handling.

Depends on

#200 for file order, and #195 for the missing pins.

Pin

LibsqlResultSetTest covers text, empty text, integer epoch millis, and REAL Julian day. #195 adds offset, Z, bare time, and BLOB rejection.

Scope

• Create SqliteDateTimeValues with from(Value, String targetType) and the static helpers from LibsqlResultSet 1156 to 1276.
• Keep a thin dateTimeValue(int, String) in the result set that calls getCurrentValue and then delegates.

Preserve

• The getCurrentValue call stays in the cursor layer. It sets lastColumnIndex, and wasNull depends on it.
• BLOB throws "Bad value for type " + targetType. Blank text returns null.
• A bare time uses 2000-01-01.
• Offsets are honored only when the sign is followed by more than nine characters. Local conversion uses ZoneId.systemDefault().
• Exception wrapping keeps the original text.

Acceptance

• SqliteDateTimeValues.java exists and holds the moved code unchanged.
• LibsqlResultSet.java is under 850 lines.
• ./mvnw -pl libsql-jdbc -am test green with no assertion edited.
• ./mvnw spotless:check green.