Implement Service Discovery Protocol

[djaboxx]

We need to implement the service discovery protocol endpoint as per the Registry API spec at /.well-known/terraform.json

Tasks:

• Implement /.well-known/terraform.json endpoint
• Return proper modules.v1 base URL with trailing slash
• Ensure all module URLs are relative to this base URL
• Update nginx config to route this endpoint correctly

Required Response should return modules.v1 with /v1/modules/ value