Update main codebase to php 8.3 syntax

[benwerd]

Here's what I fixed or added:

• Updated composer.json to require PHP 8.3, added Rector as a development dependency, and included a Composer script for running Rector.
• Created rector.php to configure Rector for PHP 8.3 syntax upgrades across the codebase.
• Implemented a new GitHub Actions workflow (.github/workflows/rector.yml) to automatically run Rector on PHP 8.3 and commit any applied upgrades.

Here's why I did it:

This PR sets up the necessary tooling and automation to bring the main codebase up to PHP 8.3 syntax. By integrating Rector and a GitHub Actions workflow, we establish an automated process for applying and maintaining PHP 8.3 compatibility, ensuring the project can leverage new language features and stay current.

Checklist: ([x] to check/tick the boxes)

• This pull request addresses a single issue
• If this code includes interface changes, I've included screenshots in this Pull Request thread
• I've adhered to Known's style guide (these codesniffer rules might help!)
• My git branch is named in a descriptive way - i.e., yourname-summary-of-issue
• I've tested my code in-browser
• My code contains descriptive comments
• I've added tests where applicable, and...
• I can run the unit tests successfully.

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[cursor]

Cursor Agent can help with this pull request. Just @cursor in comments and I'll start working on changes in this branch.
_{Learn more about Cursor Agents}

[benwerd]

This was a test PR. Closing.