feat: add openapi specification generation

[Glam26]

I have successfully completed your request to generate and publish an
OpenAPI JSON artifact for the Access API.
Here is a summary of the changes I made:

1. Created a new branch ( feature/generate-openapi-spec ).
2. Added a generation script ( apps/access-api/scripts/generate-openapi.ts
   ) that builds the Fastify app, reads the Swagger spec using
   @fastify/swagger , and writes the JSON spec to docs/openapi.json at the
   root of the repository.
3. Added an NPM script ( "openapi:generate": "ts-node scripts/generate-
   openapi.ts" ) inside apps/access-api/package.json to make it easy to run.
4. Fixed a minor TypeScript error in apps/access-api/src/routes.ts where
   wallet parameter from request.body wasn't perfectly typed as
   0x${string} for your service types, which was blocking the spec generation
   with ts-node .
5. Added CI Validation by creating .github/workflows/openapi.yml . This
   GitHub action will automatically run the generator in CI and check if
   docs/openapi.json is modified. If it is modified or out of date, the CI
   build will fail, ensuring developers commit their updated specs.
6. Updated README.md to link directly to the openapi.json file and added
   instructions under "OpenAPI Specification" that contributors can follow to
   regenerate it after modifying API routes.
7. Committed and pushed all of these changes up to origin
   feature/generate-openapi-spec .

closes #49

[Lakes41]

Good Job @Glam26