VSN-2546 — Migrate absence & document request fiches to shadcn

Summary

Fiche Congé / Absence (/dashboard/rh/absence)

• Form components: Migrated from MUI (Grid, Tabs, Tab, CircularProgress, IconButton) to shadcn (FormField, FormContainer, ActionButtons). Custom Tailwind tab bar replacing MUI Tabs.
• Layout: 3 purple section cards — Employé (User icon), Détails de la demande (FileText icon), Validation (ClipboardCheck icon). Progressive left border colors (#DBD7F9 → #C4BEF5 → #A89DF0), animate-section-in with staggered delays.
• Notifications: Replaced notistack (enqueueSnackbar) with Sonner (toast.success/error/warning).
• Icons: Replaced FontAwesome (faPaperclip) with Lucide React (Loader2, User, FileText, ClipboardCheck).
• List view: Added relative z-10 on control bar/tabs and relative z-0 on content to fix z-index overlap. Form wrapped in overflow-y-auto flex-1 min-h-0 for proper scrolling.

Fiche Demande de Document (/dashboard/rh/document)

• Form components: Migrated from MUI (Grid, Button, Stack, FontAwesomeIcon) to shadcn (FormField, FormContainer, ActionButtons, shadcn Button).
• Layout: 3 purple section cards — Demandeur (User icon), Détails de la demande (FileText icon), Suivi & Observations (ClipboardList icon). Same progressive border colors and animation pattern.
• Icons: Replaced FontAwesome (faPaperclip, faEnvelope) with Lucide React (Paperclip, Mail).
• Personnel type selector: Styled with Tailwind in the demandeur card section.
• Action buttons: shadcn Button for attach (Paperclip) and send (Mail) actions replacing MUI + FontAwesome buttons.
• List view: Same z-index and scroll fixes as absence list view.

Files modified (4)

• src/shared/sections/rh/absence/view/absence-new-view.tsx
• src/shared/sections/rh/absence/view/absence-list-view.tsx
• src/shared/sections/rh/document/view/document-form.tsx
• src/shared/sections/rh/document/view/document-list-view.tsx

Closes VSN-2546