Unify the format of export logs

[rahul0x24]

This PR includes:

• The milliseconds when converting date to string at the time of exporting the logs
• The unified export Json structure when doing any level of export (All AppRuns, Single AppRun or Single Log Entry)

A sample export json looks like this

[
  {
    "info" : {
      "appVersion" : "1",
      "device" : "iPhone12,3",
      "launchDate" : "2025-11-18T10:46:07.401Z",
      "operatingSystemVersion" : "Version 26.1 (Build 23B85)"
    },
    "logEntries" : [
      {
        "category" : "domain",
        "composedMessage" : "Not observing PTDefaults on customer install.",
        "date" : "2025-11-18T10:46:08.862Z",
        "level" : "notice",
        "subsystem" : "PrototypeTools"
      },
      {
        "category" : "App",
        "composedMessage" : "This is some detail we’d normally not care about 2025-11-18 10:46:08 am +0000",
        "date" : "2025-11-18T10:46:08.347Z",
        "level" : "debug",
        "subsystem" : "com.zuhlke.highlights"
      },
      {
        "category" : "App",
        "composedMessage" : "App initialised",
        "date" : "2025-11-18T10:46:08.344Z",
        "level" : "info",
        "subsystem" : "com.zuhlke.highlights"
      }
    ]
  }
]