ASC CLI adds Fastlane imports

This is the kind of compatibility feature that makes a CLI switch realistic: teams can preserve their existing release assets while gaining a more deterministic workflow.

• –Imports established Fastlane directory structures instead of forcing a metadata rewrite
• –`--dry-run` provides a safer review step before mutating App Store Connect
• –Paired import, export, and validate commands support a practical round-trip migration workflow
• –A single Go binary removes the need to maintain a Ruby toolchain for this part of release automation
• –The feature is especially valuable in CI, where predictable command-line behavior matters more than UI convenience