Authentication flow doesn't work with Safari

**Description**
When running `aem up` with an authenticated site the auth flow never successfully completes if your default browser is safari. When clicking send on the prompt page, an error occurs which is only surfaced via the dev console.

**To Reproduce**
Steps to reproduce the behavior:
1. make safari your default browser (my setup: safari 18.3 on Mac OS 15.3.1)
2. run `aem up` for an authenticated site with no stored site token
3. login with the IdP
4. when you arrive at `https://admin.hlx.page/auth/adobe/ack?code=...` click send
5. note that nothing happens
6. open dev tools console and note the error

**Expected behavior**
The auth flow should complete successfully. If that isn't possible due to some safari specific restriction, the user should see a message with some info on what they can do to work around.

**Screenshots**

errors from console:
```
[Warning] [blocked] The page at https://admin.hlx.page/auth/adobe/ack?code=.... requested insecure content from http://localhost:3000/.aem/cli/login/ack. This content was blocked and must (ack, line 7)

[Error] Not allowed to request resource
(anonymous function) (ack:7)
sendPost (ack:6)
(anonymous function) (ack:23)
[Error] Fetch API cannot load http://localhost:3000/.aem/cli/login/ack due to access control checks.
(anonymous function) (ack:7)
sendPost (ack:6)
(anonymous function) (ack:23)
[Error] Unhandled Promise Rejection: TypeError: Load failed
(anonymous function) (ack:7)
```

**Version:**
```
ssteimer@Seans-M3-Macbook-Pro ups % aem --version
16.10.1
```

Start at the `aem up` authentication flow and the `/auth/adobe/ack` callback described in the issue. Reproduce with Safari using an authenticated site and inspect the console error when the callback targets `http://localhost:3000/.aem/cli/login/ack`. Done means the flow completes successfully, or Safari users receive a clear actionable workaround.

Written by the indexing model from the issue text.