feat: Add Psalm static analysis to PHP Quality CI

- Add Psalm (Static Analysis) step to code-quality.yml php-quality job

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: rubenvdlinde

.github/workflows/code-quality.yml

@@ -57,6 +57,9 @@ jobs:
       - name: PHPUnit (Unit Tests)
         run: ./vendor/bin/phpunit --bootstrap tests/bootstrap-unit.php --testsuite "Unit Tests" --configuration phpunit.xml
 
+      - name: Psalm (Static Analysis)
+        run: ./vendor/bin/psalm --threads=1 --no-cache --output-format=github
+
   frontend-quality:
     name: Frontend Quality
     runs-on: ubuntu-latest