fix(home): center quick chat widget and constrain width

Chat section and inline response now have max-width 720px centered
within the page, and quick action chips are centered. Prevents the
widget from stretching the full 1200px content width on wide screens.

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

frontend/src/views/HomeView.vue

@@ -580,10 +580,14 @@ function formatUpcomingTime(event: EventEntry): string {
 }
 
 /* ─── Chat widget ────────────────────────────────────────────── */
-.chat-section { margin-bottom: 1rem; }
+.chat-section {
+  max-width: 720px;
+  margin: 0 auto 1.5rem;
+}
 .quick-actions {
   display: flex;
   flex-wrap: wrap;
+  justify-content: center;
   gap: 0.4rem;
   margin-bottom: 0.75rem;
 }
@@ -606,7 +610,8 @@ function formatUpcomingTime(event: EventEntry): string {
 
 /* ─── Inline response ────────────────────────────────────────── */
 .dashboard-response {
-  margin-bottom: 1.5rem;
+  max-width: 720px;
+  margin: 0 auto 1.5rem;
   padding: 0.75rem 1rem;
   background: var(--color-bg-card);
   border-left: 2px solid var(--color-primary);