fix(import): stream site transfer bundles and unify review flow

[DavidBabinec]

Summary

• Export site transfers as stored ZIP64 archives with .instatic/site-bundle.json first and raw media/<storagePath> files streamed from disk.
• Import Instatic transfer ZIPs through Super Import by posting the original archive to /admin/api/cms/import/archive, streaming selected media server-side instead of base64-expanding it in the browser.
• Route Instatic bundle ZIP/JSON drops into the same Super Import review category navigator used for HTML, media, styles, and scripts; removed the separate bundle-only review screen.
• Add bundle category selection for site shell, tables/rows, media, media folders, and redirects, with replace imports using the shared step-up dialog.
• Stage and validate selected archive media before applying data imports so malformed replace archives cannot wipe existing rows before failing.
• Update docs and coverage for archive routing, selection filtering, step-up retry, strict media validation, exact size estimates, and roundtrip import/export.

Why

The previous export fix made downloads start reliably, but the transfer artifact and import UI still diverged from Super Import. Large sites need a real archive path that can move media without forcing the browser or server to build a huge JSON/base64 payload, and operators should review Instatic bundles through the same category picker as other imports.

Verification

• bun test — 5508 pass, 0 fail
• bun run build
• bun run lint
• git diff --check

Notes

• Conflict with current main was resolved by removing the now-unused CmsBundleReviewStep.module.css; the shared bundle review flow uses AnalyzeStep styling.
• The archive media staging fix was added during review with a regression test covering malformed replace archives.