Dashboard: show 10 chapters titled Chapters; bump chapter mtime on beat changes

Beat create/update/delete/reorder/assign/move now touch the parent
chapter's UpdatedAt so the dashboard's recency sort reflects beat edits,
not just chapter-level prose/tag changes.

src/Novelly.Web/src/pages/DashboardPage.tsx

@@ -5,6 +5,7 @@ import { useAuth } from '../auth/AuthContext'
 import { AutoField, EmptyState, ErrorNote, Spinner, StatusBadge } from '../components/ui'
 
 const RECENT_COUNT = 5
+const RECENT_CHAPTERS_COUNT = 10
 
 export default function DashboardPage() {
   const { projectId = '' } = useParams()
@@ -61,7 +62,7 @@ function OutliningDashboard({ projectId }: { projectId: string }) {
       <div className="grid gap-6 lg:grid-cols-3">
         <section className="card p-5 lg:col-span-2">
           <div className="mb-4 flex items-center justify-between gap-4">
-            <h2 className="text-lg font-semibold">Outline</h2>
+            <h2 className="text-lg font-semibold">Chapters</h2>
             <Link to="chapters" className="text-sm muted hover:underline">
               View all →
             </Link>
@@ -74,7 +75,7 @@ function OutliningDashboard({ projectId }: { projectId: string }) {
             <EmptyState title="No chapters yet" hint="Add the first chapter to start outlining." />
           ) : (
             <ul className="grid grid-cols-1 gap-2">
-              {recentChapters.slice(0, RECENT_COUNT).map((chapter) => (
+              {recentChapters.slice(0, RECENT_CHAPTERS_COUNT).map((chapter) => (
                 <li key={chapter.id}>
                   <Link
                     to={`chapters/${chapter.id}`}