feat(provisioning): admin game-signup mode setting, invite link option, staff self-create

Follow-ups from live testing:

- Game-account creation is now an admin Settings control (disabled / website /
  hybrid / game) instead of a hidden on/off flag. The site offers creation for
  website+hybrid; help text notes the shard's SignupMode (Bridge.cfg) has the final
  say. game_account_signup setting widened to a 4-value enum + validated on save.
- Invites: the accept link is ALWAYS returned and shown with a Copy button, and a
  "Email the invitation" toggle lets an admin create a link-only invite (no email)
  or email it. Backend takes sendEmail (default true) and always returns acceptUrl.
- Staff can create a game account from their own /admin/characters page too
  (POST /admin/shard/account → the shared createGameAccount controller), so the
  form is reachable in both the player and admin portals.

Note: the admin Houses view (/admin/houses) already worked; the earlier failure
was a stale Vite HMR state for the new route (needs a hard refresh).

Client build clean; server routes load; swagger regenerated.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

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

@@ -182,6 +182,21 @@ adminRouter.get(
   /* #swagger.responses[200] = { description: 'Vendor sales', content: { "application/json": { schema: { type: "array", items: { $ref: "#/components/schemas/ShardVendorSale" } } } } } */
   selfShard.getSales,
 )
+adminRouter.post(
+  '/shard/account',
+  // #swagger.tags = ['Admin · Account']
+  // #swagger.summary = 'Create a game account and link it to the caller (staff self-service)'
+  // #swagger.description = 'Same as POST /player/shard/account but for a signed-in staff user — provisions a game account (own username + password) and links it. Gated by game_account_signup + the shard’s mode; the password is never stored or logged.'
+  // #swagger.security = [{ "cookieAuth": [] }, { "bearerAuth": [] }]
+  /* #swagger.requestBody = { required: true, content: { "application/json": { schema: { type: "object", required: ["account","password"], properties: { account: { type: "string" }, password: { type: "string" } } } } } */
+  /* #swagger.responses[201] = { description: 'Account created and linked', content: { "application/json": { schema: { type: "object", additionalProperties: true } } } } */
+  /* #swagger.responses[403] = { description: 'Game-account signup unavailable (site or shard)', content: { "application/json": { schema: { $ref: "#/components/schemas/Error" } } } } */
+  /* #swagger.responses[409] = { description: 'Account name already taken', content: { "application/json": { schema: { $ref: "#/components/schemas/Error" } } } } */
+  body('account').matches(/^[A-Za-z0-9][A-Za-z0-9_.-]{2,29}$/),
+  body('password').isString().isLength({ min: 8, max: 64 }),
+  validate,
+  selfShard.createGameAccount,
+)
 
 // ── In-game staff operations (uo-link write plane + support queue) ─────
 // Privileged live-shard actions and the help-page queue, open to moderators as