feat(api): REST API with OpenAPI for other apps, behind Pireon OAuth

A REST adapter next to GraphQL (presenters/http) that calls the same
application services, so validation, permissions and domain errors are the
same: projects (members, board, stats, activity), issues (search, workflow,
assignee, release, links, comments, history), comments, releases and users.
Projects and issues can be addressed by id or key (WEB, WEB-12).

- Swagger UI at /api/docs, document at /api/docs-json and apps/api/openapi.json
  (rewritten by `nx serve api`, like schema.gql) for client generation.
- Every route but health/auth/webhook needs a Pireon token: the document
  declares Pireon OAuth2 (authorization code + PKCE, password) through the
  /api/auth/token proxy, and a bearer scheme for apps with their own client.
- configureApp() shares main.ts setup with the e2e, which now also covers REST.
- SWAGGER_ENABLED / OPENAPI_FILE config; docs 03/05 and library READMEs.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

libs/api/identity/presenters/src/lib/identity-presenters.module.ts

@@ -5,10 +5,11 @@ import { WsAuthenticator } from './auth/ws-authenticator';
 import { UserResolver } from './graphql/user.resolver';
 import { AuthController } from './http/auth.controller';
 import { PireonWebhookController } from './http/pireon-webhook.controller';
+import { UsersController } from './http/users.controller';
 
-/** Driving adapters of the identity context: global auth guard, webhook, GraphQL. */
+/** Driving adapters of the identity context: global auth guard, REST (auth, users, webhook), GraphQL. */
 @Module({
-  controllers: [AuthController, PireonWebhookController],
+  controllers: [AuthController, UsersController, PireonWebhookController],
   providers: [
     { provide: APP_GUARD, useClass: AuthGuard },
     WsAuthenticator,