feat(server): add swagger setup for public api documentation

Introduces Swagger and OpenAPI documentation generation for the
backend API. Configures bearer authentication globally while
allowing explicit bypasses for public endpoints. Exports nested
DTO classes across several modules so the NestJS Swagger plugin
can correctly reflect their schema definitions.

Closes #399

server/README.md

@@ -10,6 +10,19 @@ Server only: `pnpm start:dev` (from this directory).
 
 The server loads environment variables from `.env` in this directory. See `.env.example` for all available options.
 
+## API docs
+
+Generated OpenAPI docs are disabled by default. Enable them with `SWAGGER_ENABLED=true`:
+
+```bash
+SWAGGER_ENABLED=true pnpm start:dev
+```
+
+Then open:
+
+- Swagger UI: http://localhost:3000/api/docs
+- OpenAPI JSON: http://localhost:3000/api/docs-json
+
 ## Module structure
 
 Each feature is a self-contained NestJS module under `src/modules/`: