feature/vsn-2710 - resolve 6 UX and data integrity bugs in role management
- Fix parent checkbox not cascading to sub-modules in permission selector
- Fix "Suivant" button hidden at standard zoom due to missing flex layout on dialog
- Fix X button non-functional; dialog now only closes on explicit user action
- Rename ambiguous "Ajouter permission personnalisée" label to "Créer une permission sur mesure"
- Fix disabled role losing its modules after status toggle due to partial backend response overwriting store
- Fix module removal not saved on edit due to a length > 0 guard silently reverting form values