DRY pass #2, batch 8, F17: a person and an account have one shape each (#5372)

Web: GroupList's Person was adapters/repo's Member field for field, and
AccountList's Account was the session store's User; both now import them.
The bridge's Identity stays, as the Tauri mirror of the core's struct.

Server: auth._serialize_user and accounts' _serialize_account wrote the same
four fields. serialize.serialize_user is serialize_person plus is_admin, and
the account list adds created_at to it.

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

frontend/src/components/GroupList.vue

@@ -1,6 +1,7 @@
 <script setup lang="ts">
 import { computed, onMounted, ref } from "vue";
 import { api } from "../api/client";
+import type { Member } from "../adapters/repo";
 import { errorMessage } from "../api/errors";
 import BaseButton from "./BaseButton.vue";
 import BaseInput from "./BaseInput.vue";
@@ -11,24 +12,18 @@ import { useRowAction, useLoad } from "../composables/useAction";
 // the instance's; anyone can share with it, and a note shared with it reaches whoever
 // is in it at the time, so adding or removing someone here changes what they see.
 
-interface Person {
-  id: string;
-  display_name: string;
-  email: string;
-}
-
 interface Group {
   id: string;
   name: string;
-  members: Person[];
+  members: Member[];
 }
 
 const groups = ref<Group[]>([]);
-const accounts = ref<Person[]>([]);
+const accounts = ref<Member[]>([]);
 const { loading, error, load } = useLoad(async () => {
   const [g, a] = await Promise.all([
     api.get<{ groups: Group[] }>("/api/groups"),
-    api.get<{ accounts: Person[] }>("/api/accounts"),
+    api.get<{ accounts: Member[] }>("/api/accounts"),
   ]);
   groups.value = g.groups;
   accounts.value = a.accounts;
@@ -41,7 +36,7 @@ const picks = ref<Record<string, string>>({});
 
 const byName = (a: Group, b: Group) => a.name.localeCompare(b.name);
 
-function outside(group: Group): Person[] {
+function outside(group: Group): Member[] {
   const inside = new Set(group.members.map((m) => m.id));
   return accounts.value.filter((a) => !inside.has(a.id));
 }
@@ -102,7 +97,7 @@ function addMember(group: Group) {
   );
 }
 
-function removeMember(group: Group, person: Person) {
+function removeMember(group: Group, person: Member) {
   void act(
     group.id,
     async () => replace(await api.del<Group>(`/api/groups/${group.id}/members/${person.id}`)),