feat: join request claim secrets, onboarding API, and company branding

Add secure claim secret flow for agent join requests with timing-safe
comparison, expiry, and one-time use. Expose machine-readable onboarding
manifests and skill index API endpoints. Add company brand color with
hex validation, pattern icon generation, and settings page integration.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/shared/src/validators/index.ts

@@ -102,11 +102,13 @@ export {
   createCompanyInviteSchema,
   acceptInviteSchema,
   listJoinRequestsQuerySchema,
+  claimJoinRequestApiKeySchema,
   updateMemberPermissionsSchema,
   updateUserCompanyAccessSchema,
   type CreateCompanyInvite,
   type AcceptInvite,
   type ListJoinRequestsQuery,
+  type ClaimJoinRequestApiKey,
   type UpdateMemberPermissions,
   type UpdateUserCompanyAccess,
 } from "./access.js";