feat(shard): admin write plane, help-page queue, and public champion board

Wire up the three uo-link sidecar surfaces that weren't integrated yet.

Champion spawns
- Ingest champ.update/champ.remove into a new shard_champs table (served from
  our own store, like online/houses); public /site/champs board with a nav link,
  live via the existing SSE feed (champ.* added to the public allowlist).

Staff write plane (admin + moderator)
- kick / ban / unban / broadcast via /admin/shard/*; actor is stamped server-side
  from the session, never the browser. Sidecar status codes mapped (403 disabled/
  protected, 404 unknown, 503/504 transient). admin.audit events are logged and
  surfaced at /admin/shard/audit.
- New admin "In-Game Ops" view (/admin/shard-ops), plus per-account Kick/Ban/Unban
  on the user-detail and character views (ShardAccountActions, self-gated to staff).

Help-page (support) queue
- Ingest page.new/updated/closed into a new shard_pages table; respond/close via
  /admin/shard/pages/*. Champ board and page queue are snapshotted from the
  sidecar's /champs and /pages on every WS (re)connect (guarded so a failed call
  never wipes local state).

Verified live end-to-end against MariaDB + the Rust sidecar + ServUO; unit tests
cover ingest routing (shardIngest.champsPages.test.js). Swagger regenerated.

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

client/src/components/SiteHeader.jsx

@@ -12,6 +12,7 @@ const NAV = [
   { label: 'Newsletter', to: '/site/newsletter' },
   { label: 'Wiki', to: '/wiki' },
   { label: 'Shard', to: '/site/shard' },
+  { label: 'Champions', to: '/site/champs' },
   { label: 'About', to: '/site/about' },
 ]