Add support for publishing posts to both feed and stories simultaneously

Introduce a new 'both' post type allowing simultaneous publishing to Facebook and Instagram feeds and stories. This includes UI updates for selecting post types, backend logic for splitting 'both' posts into separate feed and story entries, and the ability to delete scheduled posts. The changes also include a new 'Pages gérées' link in the sidebar and necessary database schema updates.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: ae4037a0-2a6f-4530-9bac-79b543286bda
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/397bca8c-984f-43ff-841a-10897aeb8140/ae4037a0-2a6f-4530-9bac-79b543286bda/WuFXYmm

client/src/components/sidebar.tsx

@@ -38,7 +38,6 @@ export default function Sidebar() {
     { icon: PlusCircle, label: "Nouvelle publication", href: "/new", badge: null },
     { icon: Calendar, label: "Calendrier", href: "/calendar", badge: null },
     { icon: Images, label: "Médiathèque", href: "/media", badge: null },
-    { icon: Users, label: "Pages gérées", href: "/pages", badge: null },
     { icon: Bot, label: "Assistant IA", href: "/ai", badge: null },
   ];
 
@@ -141,6 +140,23 @@ export default function Sidebar() {
             <div className="mb-2">
               <p className="text-xs font-semibold text-muted-foreground mb-2 px-4 uppercase tracking-wider">Administration</p>
             </div>
+            <Link 
+              href="/pages"
+              className={`
+                flex items-center gap-3 px-4 py-3 rounded-xl transition-all relative
+                ${location === "/pages"
+                  ? 'bg-gradient-to-r from-primary/10 to-secondary/10 text-primary shadow-sm' 
+                  : 'text-muted-foreground hover:bg-sidebar-accent hover:text-foreground'
+                }
+              `}
+              data-testid="link-pages-gérées"
+            >
+              {location === "/pages" && (
+                <div className="absolute left-0 top-1/2 -translate-y-1/2 w-1 h-8 gradient-primary rounded-r-full" />
+              )}
+              <Users className="w-5 h-5" />
+              <span>Pages gérées</span>
+            </Link>
             <Link 
               href="/users"
               className={`