`content-type: application/json` is missed on `/v2/api`

[davidyuk]

curl https://mainnet.aeternity.io/mdw/v2/api -I
HTTP/2 200
content-length: 171338
access-control-allow-credentials: true
access-control-allow-headers: *
access-control-allow-origin: *
access-control-expose-headers:
cache-control: max-age=0, private, must-revalidate
date: Thu, 19 Mar 2026 07:36:52 GMT
via: 1.1 Caddy, 1.1 b1fac0bf88d55c06412e298205ca1250.cloudfront.net (CloudFront)

Compared to /swagger/swagger_v2.json:

curl https://mainnet.aeternity.io/mdw/swagger/swagger_v2.json -I
HTTP/2 200
content-type: application/json
content-length: 171338
accept-ranges: bytes
access-control-allow-headers: *
access-control-allow-origin: *
cache-control: public
date: Thu, 19 Mar 2026 07:36:16 GMT
etag: "6CADE37"
via: 1.1 Caddy, 1.1 748d351622183978240f88f8fd16821c.cloudfront.net (CloudFront)