Review and reduce ExcessiveClassLength threshold in PHPMD configuration

[coderabbitai]

The current PHPMD configuration in phpmd.rules.xml sets ExcessiveClassLength minimum threshold to 2000 lines, which is quite permissive and could lead to maintainability issues.

Consider reducing this value to improve code maintainability and encourage better class design through proper separation of concerns.

Current configuration:

<rule ref="rulesets/codesize.xml/ExcessiveClassLength">
    <properties>
        <property name="minimum" value="2000" />
    </properties>
</rule>

Context:

• PR Discussion: /chore(ZMS-3414): reenable php code quality checks github actions #765#discussion_r1948971321
• PR: /chore(ZMS-3414): reenable php code quality checks github actions #765

cc @ThomasAFink