Sync stats and calendar updates using shared refresh key

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/components/Dashboard.tsx

@@ -155,7 +155,7 @@ export function Dashboard({ user }: DashboardProps) {
                 />
               </div>
               <div className="space-y-6">
-                <StatsCard usageData={usageData} substance={preferences.substance} />
+                <StatsCard key={`stats-${refreshKey}`} usageData={usageData} substance={preferences.substance} />
                 <QuitPlanCard
                   plan={preferences.quitPlan}
                   onGeneratePlan={handleGeneratePlan}