Make JSON machine readable

[beefon]

Text output is intact:

$ ./.build/debug/curie images 

REPOSITORY                    TAG     IMAGE ID         CREATED          SIZE     
myteam/myimage/test-image     2.0     c959e4645f12     3 months ago     120.03 GB
myteam/myimage/test-image     1.0     c0db27f611d0     3 months ago     120.03 GB

JSON output has been updated:

$ ./.build/debug/curie images -f json

[
  {
    "created" : "2025-09-28T20:57:10Z",        <<<< this is machine readable now
    "image_id" : "c959e4645f12",
    "repository" : "myteam\/myimage\/test-image",
    "size" : {                                 <<<< this is machine readable now
      "bytes" : 128882598851
    },
    "tag" : "2.0"
  },
  {
    "created" : "2025-09-28T20:52:34Z",
    "image_id" : "c0db27f611d0",
    "repository" : "myteam\/myimage\/test-image",
    "size" : {
      "bytes" : 128882598832
    },
    "tag" : "1.0"
  }
]

Test Plan:

• Ensure all CI checks pass
• Run both curie images and curie images -f json, verify the text version of the command prints human-friendly timestamp (e.g. 2 days ago) and JSON prints ISO8601 format

[marciniwanicki]

The change looks great, thanks @beefon! Let's fix the lint issue and if we could remove the emoji from the description and perhaps add one line about what changed and the difference tween human readable table vs json that would be great.

[marciniwanicki]

I've just noticed we have the same lint issue on main, will check it.