refactor(server): split admin shard, uo-link, email, discord-bot, settings and dashboard into capability routers

PR 4 of the in-place admin router split (docs/website/API_V2_PLAN.md § Phase 2),
and the last admin one: it moves the entire residual 33 and DELETES
admin.routes.js. Every one of the 110 admin routes is now declared in a
capability router. No URL, gate or handler changes.

  shard.router.js      (16)  /admin/shard
  uoLink.router.js     ( 5)  /admin/uo-link
  email.router.js      ( 6)  /admin/email
  discordBot.router.js ( 2)  /admin/discord-bot
  settings.router.js   ( 2)  /admin/settings
  dashboard.router.js  ( 2)  GET /dashboard + PUT /site-mode, at the group root
  admin.routes.js            deleted, was 33

No gate moved to router level. Every adminOnly in the residual file was
per-route, and modAccess on /shard must stay per-route because half that router
must not have it — which keeps the per-route handler count intact, the one
number routes.guards.json can actually check.

/shard is the first prefix where two tiers share one router: 7 self-service
account-linking routes (no extra gate, served by the same player/shard
controller handlers, tagged `Admin · Account`) alongside 9 in-game staff ops on
modAccess. Prefix ownership beats tag grouping — splitting by tag would put two
routers under one prefix for no gain. The tag mismatch stays; retagging is a
real spec diff and belongs in a PR about tags.

dashboard.router.js is the one router mounted at the group root rather than a
prefix: GET /dashboard and PUT /site-mode share no path segment. That is safe
only because the file declares no router-level middleware — a bare use(gate) in
a root-mounted router would run for every request passing through toward
another mount. The file carries a comment saying so.

Acceptance — all four gates zero-diff:
  routes.manifest.json    unchanged (200 public + 2 internal)
  routes.guards.json      unchanged (no route lost or gained a gate)
  swagger-output.json     unchanged (198 operations)
  api-route-inventory.json already in sync
plus 434 server tests green.

Verified separately, because no gate can catch it: introspecting the built
stack, all 59 literal admin paths still dispatch to their own layer — nothing
is captured first by a /:param sibling. The manifest sorts its entries, so
declaration order is invisible to it.

Also repoints the comments that referenced admin.routes.js by name
(botActivity/moderation controllers, the town-crier cap mirror in
announceJobs.logic.js) and generalizes the "the path is on the line after
router.get(" rationale in routeManifest.js, README.md and pr-checks.yml, which
was never about that one file.

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

server/scripts/routeManifest.js

@@ -11,8 +11,8 @@
  * in front of a reviewer instead of letting it slip through a "mechanical" PR.
  *
  * Runtime introspection, not source parsing: it is authoritative about mounts, and
- * the route paths in admin.routes.js sit on the line *after* `adminRouter.get(`,
- * which defeats naive greps. Not swagger-output.json either — that is annotation-
+ * a route's path sits on the line *after* `router.get(`, which defeats naive
+ * greps. Not swagger-output.json either — that is annotation-
  * derived (only annotated routes appear) and documents intent; this records reality.
  *
  * Scope: only `/api/**` and `/.well-known/**` from the public app, plus everything