fix(rh+flottes): make action icons colored and always visible, migrate RH tables to CSS grid

Summary

• Migrated absence, document, and rdv-annuel tables to CSS grid layout with shadcn components (no MUI)
• Removed bottom fade gradient from absence and document tables
• Fixed faded action icons across RH (recrutement, salarie) and Flottes (parc, marques-modèles, pétrolier, fuel card) sections
• Updated shared TableActionColumn: edit button = orange, duplicate button = blue

Changes

• rh/absence: new CSS grid table + shadcn view, no bottom fade, colored icons
• rh/document: new CSS grid table + shadcn view, 8 colored action buttons
• rh/rdv-annuel: CSS grid appointment table, MUI removed from appointment-view (FullCalendar preserved)
• rh/recrutement + salarie: removed opacity-50/hover:opacity-100 fade from all row containers
• flottes/vehicle, brand-model, fuelSupplier: same opacity fix + TableActionColumn color update