Fix queries in ONLY_FULL_GROUP_BY mode

[radarhere]

Addresses #729, building on #1129

I've searched through Jethro for any query containing 'GROUP BY' and run each of them. I found three that caused an error when ONLY_FULL_GROUP_BY mode was enabled. This addresses them, removing the requirement to disable ONLY_FULL_GROUP_BY.

I understand it has been said that this is not a priority, but thought I would offer this anyway. It is possible less queries are involved than was suspected.

[jefft]

I like this patch, as it fixes some daftness in the old code (using MySQL to calculate a date offset and then returning it for every person record). It doesn't appear to have anything to do with ONLY_FULL_GROUP_BY though?

The PHP-calculated date should be the same as MySQL-calculated, since the timezone is set the same:

jethro-pmm/include/init.php

Lines 73 to 75 in a5ceb25

	if (defined('TIMEZONE') && constant('TIMEZONE')) {
	date_default_timezone_set(constant('TIMEZONE'));
	$res = $GLOBALS['db']->query('SET time_zone = "'.date('P').'"');

It works in practice:

$ mysql -sNBe "select curdate()  + interval 7 day;"
2025-01-27
$ php -r '$ini = ["REMINDER_OFFSET" => 7]; echo $expiryDate = date("Y-m-d", strtotime($ini["REMINDER_OFFSET"] . " day")) . PHP_EOL;'
2025-01-27

[radarhere]

The error generated in master by date_reminder.php is

Syntax error or access violation: 1055 Expression #21 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'jethro.cfv.value_date' which is not functionally dependent on columns in GROUP BY clause

My change removes 'cfv.value_date' altogether.

If you like that part of this PR for non-GROUP BY reasons, I'm perfectly happy to create a separate PR with just that.