fix(shard): restrict staff in-game location to admins/moderators

The public "Staff online" list on the Shard page exposed each staff
member's in-game location (map + coordinates) to everyone, including
logged-in players and unauthenticated visitors.

Location is now privileged data:
- Server: getOnline inspects the caller's role via getUserFromRequest
  (the same non-rejecting helper siteMode uses on public routes) and
  only includes map/x/y/z for admin/moderator callers. For everyone
  else the fields are omitted from the JSON entirely, so they can't be
  read from the network tab. serial + name (online status) still shown.
- Client: Shard.jsx gates the location span on the viewer's role from
  useAuth() (same pattern as RoleGate); non-privileged viewers see who
  is online but no location field is rendered.

Tests: publicShardOnline.test.js covers admin + moderator (location
included), player + unauthenticated + editor (location omitted).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XmHdsbnLzDMAVQkAoTQSBe

server/src/router/v1/public/public.routes.js

@@ -165,7 +165,7 @@ publicRouter.get(
 publicRouter.get(
   '/shard/online',
   // #swagger.tags = ['Public · Shard']
-  // #swagger.summary = 'Staff online now (linked staff accounts; name + serial + map only)'
+  // #swagger.summary = 'Staff online now (linked staff accounts; location is admin/moderator-only)'
   /* #swagger.responses[200] = { description: 'Online players', content: { "application/json": { schema: { type: "array", items: { $ref: "#/components/schemas/ShardOnlinePlayer" } } } } } */
   shard.getOnline,
 )