[3.0] Makes the settings counters increment on PostgreSQL too

[albertlast]

Description

Config::updateModSettings($array, true) supports true and false as values, meaning "increment" and "decrement". It builds this:

UPDATE {db_prefix}settings
SET value = value + 1
WHERE variable = {string:variable}

settings.value is a text column. MySQL coerces it and the counter goes up. PostgreSQL refuses:

ERROR:  operator does not exist: text + integer
HINT:  No operator matches the given name and argument types.

Nothing then happens. The PostgreSQL API discards failed statements without logging or raising (see #9341), so the query simply does nothing and the request carries on. Four counters go through this path — totalMessages, totalTopics, totalMembers and unapprovedMembers — and on PostgreSQL none of them have been moving. They only ever look right after a manual recount in Forum Maintenance, until the next post pushes them out of step again.

Easy to see on a PostgreSQL install:

smf=# SELECT (SELECT value FROM smf_settings WHERE variable='totalMessages'),
smf-#        (SELECT COUNT(*)::text FROM smf_messages);
 value | count
-------+-------
 4     | 5

Casting into DECIMAL and back out through CONCAT() is accepted by both databases and keeps the increment a single atomic statement, so two simultaneous posts still cannot lose a count:

SET value = CONCAT(CAST(value AS DECIMAL) + 1, '')

Testing

Docker environment, PostgreSQL 17. Before the change, posting a reply left totalMessages at 4 with 5 rows in smf_messages. After it, each new post moves the counter, a new topic moves totalTopics, and Forum Maintenance → recount agrees with the live totals (7 and 7).

Verified the expression on both engines directly:

postgres:  SELECT CONCAT(CAST('4' AS DECIMAL) + 1, '');  ->  5  (text)
mysql:     SELECT CONCAT(CAST('4' AS DECIMAL) + 1, '');  ->  5

vendor/bin/phpunit — 108 tests, 157 assertions, OK.

Issues References (Fixes|Related|Closes)

Related to #9341