fix(auth): use org token region_url as API base URL

[shayna-ch]

Org auth tokens embed both url (always the primary US URL) and region_url, but the CLI only read url. For orgs with non-default data residency (e.g. EU), uploads routed to the wrong region and failed with Invalid org token, ignoring SENTRY_URL/--url.

Now prefers region_url as the API base URL when present, falling back to url for older tokens.

[github-actions]

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### Fixes

- use org token region_url as API base URL ([#3377](https://github.com/getsentry/sentry-cli/pull/3377))

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