The organizational chart functionality is being folded into the main HR app, simplifying how employee hierarchy features are delivered and maintained. This is an internal restructuring, so users should see the same capabilities with a more consolidated HR setup.

This commit merges the hr_org_chart module into hr.

task-4925995

The Planning app’s contract-related Gantt chart code has been moved into the main Planning Gantt area. This keeps related scheduling code together, making future maintenance easier without changing the user-facing planning experience.

After the HR refactoring, `planning_hr_contract` was merged into the `planning` module. However, its JS customizations remained in a separate `planning_contract_gantt` folder. This commit moves that code into the `planning_gantt` folder to centralize all Gantt logic.

task-4926655