Release v1.0.0.16

Add timed, apply and remove attribute commands; build on Java 25

Add /attributioner timed <player> <attribute> <amount> <operation> <seconds>
for applying a modifier that is removed by a scheduled task. Repeating it for
the same attribute replaces the modifier and restarts the timer. Add
/attributioner apply and /attributioner remove for manual modifiers. Both use
keys under the attributioner- prefix so the existing join/quit/reload cleanup
still removes them.

Look up attributes through Paper's attribute registry instead of the
deprecated Attribute.valueOf()/values(), gate the command on
attributioner.admin only, add tab completion and a full help listing, and
update the README.

Build with a Java 25 toolchain targeting Java 25, update the Gradle wrapper to
9.7.1 and run CI on Java 25.