Localizable.xcstrings and Generated/L10n.swift are generated from
localization/strings.json — the single source of truth — yet were committed,
which caused redundant tracking and a spurious ~10k-line diff every time
Xcode reformatted the catalog on build.
Treat them like the (already gitignored) Rust bindings: generate at build
time instead of tracking them. gitignore both; make the `apple-project`
target depend on `localization` so `bun run generate` recreates them before
xcodegen; install Bun in the Apple CI job and trigger it on localization/**.
Android strings.xml stays tracked — it has no reformatting churn and its
build doesn't run the generator.
- Introduce a CoreGateway protocol so feature models depend on a seam
(CoreRepository conforms); enables faking the core in tests
- Add a VniDropTests target with 42 tests mirroring the KMP suites:
approval coordinator, send/receive/settings/app models, preferences,
file previews, invitation decode, message queue, error mapping
- Add a fake gateway/file-system/device-info and fixtures
- Add .github/workflows/apple.yml: build the Rust core, generate the
project, and run the tests on an iOS Simulator
