feat(import): add collection select all

[santosli]

Summary

• add a native per-collection checkbox that toggles every eligible child across the complete collection
• expose checked, unchecked, and native indeterminate selection states with accessible counts
• preserve blocked, imported, system, conflicted, unresolved-type, standalone, and other-collection selections

Validation

• node --test apps/desktop/src/App.import-candidates.test.js apps/desktop/src/cardLayout.test.js
• npm test
• npm --workspace apps/desktop run build
• npm audit --audit-level=high
• git diff --check
• visual QA at 1600x900 and 1000x760