feat(layout): login, uygulama kabuğu, alt menü, hızlı ekle ve dashboard

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/components/page-header.tsx

@@ -0,0 +1,20 @@
+/** Sayfa başlığı + açıklama + sağda isteğe bağlı aksiyonlar. */
+export function PageHeader({
+  title,
+  description,
+  actions,
+}: {
+  title: string;
+  description?: string;
+  actions?: React.ReactNode;
+}) {
+  return (
+    <div className="flex flex-wrap items-end justify-between gap-3">
+      <div className="min-w-0">
+        <h1 className="text-2xl font-semibold tracking-tight">{title}</h1>
+        {description ? <p className="mt-1 text-sm text-muted-foreground">{description}</p> : null}
+      </div>
+      {actions ? <div className="flex items-center gap-2">{actions}</div> : null}
+    </div>
+  );
+}