feat: add PageHeader component and centralize page spacing

- Create reusable PageHeader component (emoji + title + subtitle + actions)
- Use PageHeader in sessions, teams, users, objectives pages
- Centralize vertical padding in layout (py-6) and remove per-page py-* values

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/sessions/page.tsx

@@ -24,7 +24,7 @@ import {
   getGifMoodSessionsByUserId,
   getTeamCollaboratorSessionsForAdmin as getTeamGifMoodSessions,
 } from '@/services/gif-mood';
-import { Card } from '@/components/ui';
+import { Card, PageHeader } from '@/components/ui';
 import { withWorkshopType } from '@/lib/workshops';
 import { WorkshopTabs } from './WorkshopTabs';
 import { NewWorkshopDropdown } from './NewWorkshopDropdown';
@@ -113,22 +113,17 @@ export default async function SessionsPage() {
   const totalCount = allSessions.length;
 
   return (
-    <main className="mx-auto max-w-7xl px-4 py-8 sm:py-12">
-      {/* Header */}
-      <div className="mb-10 flex flex-col sm:flex-row sm:items-end justify-between gap-6">
-        <div>
-          <div className="flex items-center gap-3 mb-1.5">
-            <h1 className="text-3xl font-bold tracking-tight text-foreground">Mes Ateliers</h1>
-            {totalCount > 0 && (
-              <span className="inline-flex items-center justify-center px-2.5 h-6 rounded-full bg-primary/10 text-primary text-sm font-semibold">
-                {totalCount}
-              </span>
-            )}
-          </div>
-          <p className="text-sm text-muted">Tous vos ateliers en un seul endroit</p>
-        </div>
-        <NewWorkshopDropdown />
-      </div>
+    <main className="mx-auto max-w-7xl px-4">
+      <PageHeader
+        emoji="🗂️"
+        title="Mes Ateliers"
+        subtitle={
+          totalCount > 0
+            ? `${totalCount} atelier${totalCount > 1 ? 's' : ''} · Tous vos ateliers en un seul endroit`
+            : 'Tous vos ateliers en un seul endroit'
+        }
+        actions={<NewWorkshopDropdown />}
+      />
 
       {/* Content */}
       {hasNoSessions ? (