build(apple): stop tracking generated localization outputs

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.

apple/project.yml

@@ -1,6 +1,9 @@
 # XcodeGen spec for the native SwiftUI VniDrop app (iOS/iPadOS/macOS).
 # Regenerate the project with:  xcodegen generate  (run from apple/)
-# Requires the Rust core first:  apple/scripts/build-core.sh debug
+# Requires two generated inputs first (both gitignored), before xcodegen:
+#   - Rust core:      apple/scripts/build-core.sh debug
+#   - Localization:   (cd localization && bun run src/cli.ts generate)
+#                     -> VniDrop/Resources/Localizable.xcstrings, VniDrop/Generated/L10n.swift
 name: VniDrop
 options:
   bundleIdPrefix: com.vnidrop