feat(lustre): add keyed application host

[GG-O-BP]

Summary

• add glendix/lustre.keyed_host, a typed props-and-render API that preserves a hosted application for an unchanged key and remounts it when the key changes
• use redraw.keyed for React key assignment while keeping the minimal stable hook-owning host inside the existing Lustre FFI boundary
• add focused React lifecycle contracts for initial mount, unchanged key, fresh props, changed key, cleanup, empty keys, and nested Lustre/Redraw embedding
• document the package-backed approach in English, Korean, and Japanese, including why directly keying an evaluated use_tea result and lustre/element/keyed do not provide host-level remounting

Ecosystem boundary

Redraw provides key assignment, but use_tea invokes hooks while its element is being produced. A key applied only after that evaluation cannot remount the hook owner. The small existing-boundary KeyedHost defers the render callback into a stable React component; redraw.keyed then keys that component. No new FFI file or application-specific datasource logic is introduced.

Verification

• ./scripts/verify.sh inner glendix
• GLENDIX_MENDIX_URL=http://127.0.0.1:18080 ./scripts/verify.sh final
  • the isolated verification checkout used alternate mxcli app/admin/serve ports because port 8080 was occupied by an external listener; no committed source was changed for this workaround
• reference consumer (GG-O-BP/mendix-ironcalc-spreadui) with its local SpreadUiHost/keyed_host JavaScript removed and this branch used as a path dependency:
  • gleam format --check src test
  • gleam check
  • gleam build --warnings-as-errors
  • gleam test --runtime bun
  • bun test test/*.test.mjs
  • gleam run -m glendix/install --runtime bun
  • gleam run -m glendix/build --runtime bun

Closes #6