feat(absences) : avancement module absences + suppression du portail client

Deux lots regroupés sur la branche feat/absence-management.

Suppression complète du portail client :
- retire ROLE_CLIENT (security.yaml) ; User::getRoles() ajoute toujours ROLE_USER
- supprime l'entité ClientTicket (+ repo, states, relations), User.client et
  User.allowedProjects, NotificationService, ProjectAllowedExtension, le bloc
  ROLE_CLIENT de MailAccessChecker
- front : pages /portal, layout portal, composants client-ticket/,
  AdminClientTicketTab, services/dto/i18n/docs associés
- fixtures : retire les users client-liot / client-acme
- migration Version20260522110000 (drop client_ticket, user_allowed_projects,
  colonnes liées ; task_document.task_id -> NOT NULL)
- tests : retire les cas obsolètes testant le blocage des clients sur le mail

Module gestion des absences (WIP) :
- entités / migrations (Version20260521160000, Version20260522090000)
- pages absences.vue / team-absences.vue, composants frontend/components/absence/
- services front, AccrueLeaveCommand, PublicHolidayController

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/pages/help.vue

@@ -20,7 +20,6 @@ const META: Record<string, { title: string, icon: string, accent: string, roles:
     '03-my-tasks':           { title: 'Mes tâches',           icon: 'mdi:checkbox-marked-circle-outline', accent: 'from-sky-500 to-cyan-500',        roles: ['admin', 'user'] },
     '04-time-tracking':      { title: 'Time tracking',        icon: 'mdi:timer-outline',                   accent: 'from-emerald-500 to-teal-500',    roles: ['admin', 'user'] },
     '05-tasks-detail':       { title: 'Tâches en détail',     icon: 'mdi:file-document-edit-outline',      accent: 'from-violet-500 to-purple-600',  roles: ['admin', 'user'] },
-    '06-client-portal':      { title: 'Portal client',        icon: 'mdi:account-tie-outline',             accent: 'from-orange-500 to-amber-500',   roles: ['admin', 'client'] },
     '07-admin':              { title: 'Administration',       icon: 'mdi:shield-crown-outline',            accent: 'from-rose-500 to-pink-600',      roles: ['admin'] },
     '08-integrations':       { title: 'Intégrations',         icon: 'mdi:puzzle-outline',                  accent: 'from-blue-500 to-indigo-500',    roles: ['admin', 'user'] },
     '09-mcp-api':            { title: 'Token MCP & API',      icon: 'mdi:robot-outline',                   accent: 'from-slate-700 to-slate-900',    roles: ['admin', 'user'] },
@@ -40,7 +39,6 @@ const auth = useAuthStore()
 const userRole = computed<'admin' | 'user' | 'client'>(() => {
     const roles = auth.user?.roles ?? []
     if (roles.includes('ROLE_ADMIN')) return 'admin'
-    if (roles.includes('ROLE_CLIENT')) return 'client'
     return 'user'
 })