Refonte UI : design system, logo, shell responsive et pages simples

- Nouveaux tokens (indigo/corail, statuts, plateformes) et mode sombre
- Logo et favicon Social Flow redessinés
- AppShell partagé : sidebar groupée (desktop) + barre de navigation basse (mobile)
- Suppression des pages mobiles dupliquées et des composants morts
- Tableau de bord, connexion, 404, calendrier, médiathèque, IA, statistiques

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017ADkrVcVFTT14hbB148HYS

client/src/components/ui/tabs.tsx

@@ -12,7 +12,7 @@ const TabsList = React.forwardRef<
   <TabsPrimitive.List
     ref={ref}
     className={cn(
-      "inline-flex h-10 items-center justify-center rounded-md bg-muted p-1 text-muted-foreground",
+      "inline-flex h-10 items-center justify-center rounded-lg bg-muted p-1 text-muted-foreground",
       className
     )}
     {...props}
@@ -27,7 +27,7 @@ const TabsTrigger = React.forwardRef<
   <TabsPrimitive.Trigger
     ref={ref}
     className={cn(
-      "inline-flex items-center justify-center whitespace-nowrap rounded-sm px-3 py-1.5 text-sm font-medium ring-offset-background transition-all focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 disabled:pointer-events-none disabled:opacity-50 data-[state=active]:bg-background data-[state=active]:text-foreground data-[state=active]:shadow-sm",
+      "inline-flex items-center justify-center whitespace-nowrap rounded-md px-3 py-1.5 text-sm font-medium ring-offset-background transition-all focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 disabled:pointer-events-none disabled:opacity-50 data-[state=active]:bg-card data-[state=active]:text-foreground data-[state=active]:shadow-sm",
       className
     )}
     {...props}