- Add `files` and `manifest` to CompanyPortabilityPreviewResult so the
import UI can show actual file contents and metadata
- Rewrite import preview as a file/folder tree (matching export page
design language) with per-file checkboxes to include/exclude items
- Show action badges (create/update/skip) on each file based on the
import plan, with unchecked files dimmed and badged as "skip"
- Add rich frontmatter preview: clicking a file shows parsed frontmatter
as structured data (name, title, reportsTo, skills) plus markdown body
- Include skills count in the sidebar summary
- Update import button to show dynamic file count that updates on
check/uncheck
- Both /tree/ and /blob/ GitHub URLs already supported by backend
Co-Authored-By: Paperclip <noreply@paperclip.ing>