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>

apps/api/src/main.ts

@@ -1,22 +1,19 @@
-import { Logger, ValidationPipe } from '@nestjs/common';
+import { Logger } from '@nestjs/common';
 import { NestFactory } from '@nestjs/core';
-import { DomainErrorFilter } from '@task-stream/api/shared/presenters';
 import { AppModule } from './app/app.module';
+import { configureApp } from './app/configure';
 
 async function bootstrap() {
   // rawBody: needed to verify Pireon webhook signatures.
   const app = await NestFactory.create(AppModule, { rawBody: true });
-  app.setGlobalPrefix('api');
-  app.enableCors();
-  app.enableShutdownHooks();
-  app.useGlobalPipes(new ValidationPipe({ transform: true, whitelist: true }));
-  app.useGlobalFilters(new DomainErrorFilter());
+  configureApp(app);
 
   const port = process.env['PORT'] || 3000;
   await app.listen(port);
   Logger.log(
     `🚀 GraphQL: http://localhost:${port}/graphql (ws for subscriptions)`,
   );
+  Logger.log(`📘 REST:    http://localhost:${port}/api/docs (OpenAPI)`);
   Logger.log(`❤️  Health:  http://localhost:${port}/api/health`);
 }