feat: admin Visas tab — table + edit dialog + visibility toggle

Activates the previously-disabled Visas tab on /admin/logistics.

VisasTab renders a flat table joined per attendee per project, sorted
by status priority. Status filter pills mirror the Confirmations tab.
The header carries a "Visible to teams" Switch backed by a new
logistics.getVisaVisibility query and the existing setVisaVisibility
mutation; toggling it controls whether members see their own status.

VisaEditDialog is a per-row editor with a status dropdown,
nationality input, three native date inputs (invitation / appointment
/ decision), and a notes textarea. No file uploads — the platform
deliberately holds zero document artifacts.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/app/(admin)/admin/logistics/page.tsx

@@ -16,6 +16,7 @@ import {
 import { ConfirmationsTab } from '@/components/admin/logistics/confirmations-tab'
 import { TravelTab } from '@/components/admin/logistics/travel-tab'
 import { HotelsTab } from '@/components/admin/logistics/hotels-tab'
+import { VisasTab } from '@/components/admin/logistics/visas-tab'
 
 export default function LogisticsPage() {
   const { currentEdition } = useEdition()
@@ -50,9 +51,8 @@ export default function LogisticsPage() {
           <TabsTrigger value="hotels">
             <HotelIcon className="mr-2 h-4 w-4" /> Hotels
           </TabsTrigger>
-          <TabsTrigger value="visas" disabled>
+          <TabsTrigger value="visas">
             <Stamp className="mr-2 h-4 w-4" /> Visas
-            <span className="text-muted-foreground ml-1 text-xs">(soon)</span>
           </TabsTrigger>
           <TabsTrigger value="lunch" disabled>
             <Salad className="mr-2 h-4 w-4" /> Lunch
@@ -81,6 +81,9 @@ export default function LogisticsPage() {
         <TabsContent value="hotels">
           <HotelsTab programId={programId} />
         </TabsContent>
+        <TabsContent value="visas">
+          <VisasTab programId={programId} />
+        </TabsContent>
       </Tabs>
     </div>
   )