Add timezone display to admin Next.js frontend

Display user timezone in:
- Notification Preferences table (new Timezone column)
- User detail page (Basic Information card)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

admin/src/app/(dashboard)/notification-prefs/page.tsx

@@ -193,6 +193,15 @@ export default function NotificationPrefsPage() {
         />
       ),
     },
+    {
+      accessorKey: 'timezone',
+      header: 'Timezone',
+      cell: ({ row }) => (
+        <span className="text-sm">
+          {row.original.timezone || <span className="text-muted-foreground">-</span>}
+        </span>
+      ),
+    },
     {
       id: 'notification_times',
       header: () => (

admin/src/app/(dashboard)/users/[id]/client.tsx

@@ -239,6 +239,12 @@ export function UserDetailClient() {
                 </div>
                 <div>{new Date(user.date_joined).toLocaleDateString()}</div>
               </div>
+              <div>
+                <div className="text-sm font-medium text-muted-foreground">
+                  Timezone
+                </div>
+                <div>{user.timezone || '-'}</div>
+              </div>
             </div>
           </CardContent>
         </Card>

admin/src/lib/api.ts

@@ -652,6 +652,8 @@ export interface NotificationPreference {
   task_overdue_hour: number | null;
   warranty_expiring_hour: number | null;
   daily_digest_hour: number | null;
+  // User timezone (IANA name, auto-captured from X-Timezone header)
+  timezone: string | null;
   created_at: string;
   updated_at: string;
 }

admin/src/types/models.ts

@@ -28,6 +28,7 @@ export interface User {
 export interface UserDetail extends User {
   residences?: ResidenceSummary[];
   devices?: DeviceSummary[];
+  timezone?: string; // IANA timezone (auto-captured from mobile app)
 }
 
 export interface ResidenceSummary {