[3.0] Imports the UserDataset enum that PM.php has been using without it

[albertlast]

Description

Sending a personal message fails outright on current release-3.0:

Class "SMF\PersonalMessage\UserDataset" not found

Sources/PersonalMessage/PM.php uses UserDataset::Minimal and UserDataset::None at lines 1607, 1670 and 1917, but the file never imports the enum. Its own namespace is SMF\PersonalMessage, so an unqualified name resolves there rather than to SMF\UserDataset.

PM::send() gets as far as User::load($all_to, dataset: UserDataset::Minimal) when it goes to load the recipients, and dies. The message is not stored and the sender lands on an error page. Nothing in the class is guarded against it, so it happens every time, on both databases and on every theme.

One line: use SMF\UserDataset;.

Testing

Docker environment, PostgreSQL 17. Before: composing a PM and pressing "Send message" produced the "Class not found" error page, smf_personal_messages unchanged, and a general row in log_errors. After: the PM is delivered, the sender is redirected to the inbox with done=sent, the row is in smf_personal_messages, and the error log stays empty.

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

Found while checking what the PostgreSQL error reporting in #9341 exposed. This one is not a query failure and is unrelated to that change; it just turned up on the way past.

The report in #9308 also mentions that the recipient autocomplete does not complete the way 2.1 does. That part does not reproduce here: on the same tree, typing into the To field returns an auto_suggest_div populated from action=suggest as expected. Whatever is behind that half of the report is separate from this fix.

Issues References (Fixes|Related|Closes)

Fixes #9308
Related to #9341