Photo du bénévole ajoutée par la coordination

Section « Photo » sur la fiche bénévole (ajouter / remplacer / retirer),
PUT/DELETE /editions/{id}/volunteers/{vid}/photo (COORDINATION),
validation de l'image partagée avec le formulaire public (read_photo).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/api/mock/mock-client.ts

@@ -1069,6 +1069,21 @@ export function createMockApi(): PlanningApi {
         if (!dataUrl) return null;
         return (await fetch(dataUrl)).blob();
       },
+      setPhoto: async (_edition, id, file) => {
+        const v = state.volunteers.find((x) => x.id === id) ?? notFound();
+        if (!['image/png', 'image/jpeg'].includes(file.type)) {
+          throw new ApiError(422, 'form.photo_type_not_supported');
+        }
+        state.photos.set(id, await fileToDataUrl(file));
+        Object.assign(v, { has_photo: true, updated_at: touch() });
+        return delay(v);
+      },
+      removePhoto: (_edition, id) => {
+        const v = state.volunteers.find((x) => x.id === id) ?? notFound();
+        state.photos.delete(id);
+        Object.assign(v, { has_photo: false, updated_at: touch() });
+        return delay(v);
+      },
       exportXlsx: () => delay(MOCK_XLSX_BLOB()),
       exportMecenatReceipts: () => {
         const paid = state.volunteers.some(