Make right column cards fill height to align with Upcoming card

Wrap TodoWidget in flex-1 container and add h-full to its Card so
the Upcoming Todos card stretches to fill remaining space in the
right column, keeping both columns visually aligned.

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

frontend/src/components/dashboard/DashboardPage.tsx

@@ -199,9 +199,11 @@ export default function DashboardPage() {
                 <CountdownWidget events={data.starred_events} />
               )}
               <CalendarWidget events={data.todays_events} />
+              <div className="flex-1">
                 <TodoWidget todos={data.upcoming_todos} />
               </div>
             </div>
+          </div>
 
           {/* Active Reminders — exclude those already shown in alert banner */}
           {(() => {

frontend/src/components/dashboard/TodoWidget.tsx

@@ -33,7 +33,7 @@ export default function TodoWidget({ todos }: TodoWidgetProps) {
   const navigate = useNavigate();
 
   return (
-    <Card>
+    <Card className="h-full">
       <CardHeader>
         <CardTitle className="flex items-center gap-2">
           <div className="p-1.5 rounded-md bg-blue-500/10">