feat(server): add Swagger API docs (#13455)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Interactive API documentation available at /api/docs when running in
development.

* **Chores**
* Added a development dependency to enable generation of the API
documentation.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: DarkSky <25152247+darkskygit@users.noreply.github.com>
Co-authored-by: DarkSky <darksky2048@gmail.com>

packages/backend/server/package.json

@@ -128,6 +128,7 @@
     "@affine-tools/utils": "workspace:*",
     "@affine/graphql": "workspace:*",
     "@faker-js/faker": "^10.0.0",
+    "@nestjs/swagger": "^11.2.0",
     "@nestjs/testing": "patch:@nestjs/testing@npm%3A10.4.15#~/.yarn/patches/@nestjs-testing-npm-10.4.15-d591a1705a.patch",
     "@types/cookie-parser": "^1.4.8",
     "@types/express": "^5.0.1",