Fix import statements (default → named exports)

[andreiborza]

Fix import statements throughout codebase:

// Old
import SentryCli, {SentryCliReleases} from '@sentry/cli';
// New
import { SentryCli } from '@sentry/cli';

• Update src/cli.ts and any other files using imports
• Remove usage of SentryCliReleases type if present

[linear]

CLI-275