fix(logistics): Hotels tab crash — Radix SelectItem cannot have empty value

The 'Unassigned' rooming option used value="" which throws at runtime
(blank tab behind the error boundary). Use a sentinel value mapped to unassign.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components/admin/logistics/hotels-tab.tsx

@@ -38,6 +38,10 @@ import {
 } from '@/components/ui/select'
 import { Download, ExternalLink, Hotel as HotelIcon, Loader2, Plus, Trash2, Pencil } from 'lucide-react'
 
+// Radix <SelectItem> forbids an empty-string value, so the "unassigned" option
+// uses this sentinel; handleHotelChange maps it back to an unassign.
+const UNASSIGN_VALUE = '__unassign__'
+
 interface Props {
   programId: string
 }
@@ -439,7 +443,7 @@ function AttendeeRoomRow({
   const currentHotelId = row.stay?.hotelId ?? ''
 
   const handleHotelChange = (value: string) => {
-    if (!value) {
+    if (!value || value === UNASSIGN_VALUE) {
       unassignMutation.mutate({ attendingMemberId: row.attendingMemberId })
     } else {
       assignMutation.mutate({
@@ -506,7 +510,7 @@ function AttendeeRoomRow({
           <SelectValue placeholder="— Unassigned —" />
         </SelectTrigger>
         <SelectContent>
-          <SelectItem value="">— Unassigned —</SelectItem>
+          <SelectItem value={UNASSIGN_VALUE}>— Unassigned —</SelectItem>
           {hotels.map((h) => (
             <SelectItem key={h.id} value={h.id}>
               {h.name}