Update documentation for Workflow for Employee Onboarding

[dimas9009]

Updated the "Configuring a Workflow in Studio Pro for the Employee Onboarding Process" how-to (refguide/workflow-how-to-configure) with current Studio Pro UI screenshots and revised instructions.

Text changes:

• Renamed EmployeesToOnboard page to EmployeeOnboarding_Overview throughout
• Renamed Add button to New Employee onboarding
• Updated "Call workflow" button drag-and-drop steps — dialog now appears automatically after drop
• Added step to open workflow from App Explorer before adding activities
• Updated Targeted Users section — replaced old "Target users using XPath" with new "Target → User(s)" UI
• Added instruction to switch to XPath expression mode in the constraint editor
• Updated visibility dialog steps with new Condition for visibility UI
• Added Atlas_Core to module roles assignment
• Added Default rights for new members step in entity access rules
• Replaced microflow selection with creation flow (New → name → OK)
• Added View App button description with default login credentials (MxAdmin / 1)
• Added new section: Configuring the Navigation Menu with full step-by-step instructions
• Added info block explaining page visibility based on WorkflowCommons role mapping
• Reorganized Testing section — moved Run Locally / View App steps to the top

Image changes:

• Replaced 20 existing screenshots with updated Studio Pro UI
• Added 9 new screenshots (select-workflow-dialog, xpath-expression, visibility-condition, view-app, manager-role, menu-structure, select-page-navigation, icons-for-navigation, admin-center)
• Removed obsolete demo_hr.png

[CLAassistant]

All committers have signed the CLA.