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/app/health.controller.ts

@@ -5,12 +5,19 @@ import {
   ServiceUnavailableException,
 } from '@nestjs/common';
 import { InjectConnection } from '@nestjs/mongoose';
+import {
+  ApiOkResponse,
+  ApiOperation,
+  ApiServiceUnavailableResponse,
+  ApiTags,
+} from '@nestjs/swagger';
 import { Public } from '@task-stream/api/identity/presenters';
 import { REDIS_CLIENT } from '@task-stream/api/shared/infrastructure';
 import Redis from 'ioredis';
 import { Connection } from 'mongoose';
 import { DataSource } from 'typeorm';
 
+@ApiTags('Health')
 @Controller('health')
 export class HealthController {
   constructor(
@@ -21,6 +28,13 @@ export class HealthController {
 
   @Public()
   @Get()
+  @ApiOperation({ summary: 'API and databases status' })
+  @ApiOkResponse({
+    schema: {
+      example: { status: 'ok', postgres: 'up', mongo: 'up', redis: 'up' },
+    },
+  })
+  @ApiServiceUnavailableResponse({ description: 'A database is down' })
   async check() {
     const checks = await Promise.allSettled([
       this.postgres.query('SELECT 1'),