feat(admin): view a user's shard footprint at /admin/users/:id

Add a "View" action beside Edit in the users table that opens a dedicated,
read-only page showing everything the uo-link shard knows about a user,
scoped to their linked game accounts: character rosters, currently-online
characters, houses (IDOC-first), and recent vendor sales.

Backend (admin-only, under the existing /users adminOnly gate):
- GET /admin/users/:id — single sanitized user (page is deep-linkable)
- GET /admin/users/:id/shard/{accounts,sales,houses,online}
- shardState: listHousesByAccounts / listOnlineByAccounts (+ model shapers)
- Extract salesForAccounts into utils/shardSales; reuse in player getSales
- Live rosters reuse the existing admin-bypass /admin/shard/* endpoints,
  so no new routes for roster/vendors/char

Frontend:
- UserDetail page reusing CharacterStats / GameAccounts / VendorSales
- GameAccounts gains a readOnly prop (drops link form + self-voice copy)
- api.admin.getUser + api.admin.userShard(id) scope; route + layout title

Tests: adminUserShard.test.js (404, account scoping, empty accounts,
salesForAccounts cap/filter). Full server suite 164 pass; client builds.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0114TpmrNW4wNXsHq5CR72jQ

client/src/routes/admin/views/UsersAdmin.jsx

@@ -1,4 +1,5 @@
 import { useCallback, useState } from 'react'
+import { useNavigate } from 'react-router-dom'
 import { Loading, ErrorState } from '../../../components/PageState.jsx'
 import { useAsync } from '../../../lib/useAsync.js'
 import { dateTime } from '../../../lib/format.js'
@@ -13,6 +14,7 @@ const ROLE_BADGE = {
 }
 
 export default function UsersAdmin() {
+  const navigate = useNavigate()
   const [tick, setTick] = useState(0)
   const reload = useCallback(() => setTick((t) => t + 1), [])
   const { loading, error, data } = useAsync(() => api.admin.listUsers(), [tick])
@@ -64,8 +66,13 @@ export default function UsersAdmin() {
                   </td>
                   <td className="adm-td dim">{u.last_login_at ? dateTime(u.last_login_at) : 'never'}</td>
                   <td className="adm-td" style={{ textAlign: 'right' }}>
-                    <span className="link-accent" onClick={() => setEditing(u)}>
-                      Edit
+                    <span style={{ display: 'inline-flex', gap: 16, justifyContent: 'flex-end' }}>
+                      <span className="link-accent" onClick={() => navigate(`/admin/users/${u.id}`)}>
+                        View
+                      </span>
+                      <span className="link-accent" onClick={() => setEditing(u)}>
+                        Edit
+                      </span>
                     </span>
                   </td>
                 </tr>