feat(translation): add post-ASR translation mode for cloud engine

Adds an opt-in translation pipeline that reuses the existing
PolishingService + LLMClient + AppGroupStore chain. Translation is
implemented as a new PolishMode (.translate(targetLocaleId:)); all
existing call sites are unchanged.

Settings:
- New TranslationPickerRow in the language tab (Toggle + 10-locale
  picker: en/zh-Hans/zh-Hant/ja/ko/fr/de/es/ru/pt), persisted to the
  App Group so the keyboard extension can read it during live dictation.
- 5 new strings per language (en + zh-Hans).

Keyboard:
- New TranslationChip on the top bar to the right of LocaleChip;
  same Menu pattern, lets users toggle or quickly switch target
  language without leaving the keyboard.
- PolishingService dispatches .translate with a parameterised prompt
  (en/zh variants selected by provider id); PolishingService.error
  gains a translationNotAvailable case so local-engine users get a
  clear inline warning when the toggle is on but cloud is off.
- 6 new strings per language (en + zh-Hans) for the chip + banner.

Local engine policy:
- Translation is cloud-only by design (local engine stays ASR-only
  to honour the no-roundtrip promise). Chip shows a 'cloud required'
  state and raw transcript still inserts on failure — no data loss.

Build:
- OSGKeyboardShared adds TranslationLanguage enum (10 locales) and
  TranslationPrompt factory.
- 4 new files, 9 modified. xcodebuild scheme=OSGKeyboard
  config=Debug destination=iPhone 17 Simulator: BUILD SUCCEEDED
  (0 warning, 0 error).

Also pins DEVELOPMENT_TEAM in project.yml for TestFlight uploads
(3 targets; Team X329MZU23S).

OSGKeyboardShared/Services/KeyboardState.swift

@@ -87,6 +87,20 @@ public final class KeyboardState: ObservableObject {
     /// CoreML local engine. Always `false` now — there are no weights
     /// for the host app to preload.
     @Published public var localModelsLoaded: Bool = false
+    /// v0.2.1: translation toggle mirrored from `ProviderConfig`. The
+    /// pipeline asks `isTranslationEffective` before honouring it —
+    /// the local engine ignores translation regardless of this flag.
+    @Published public var translationEnabled: Bool = false
+    /// v0.2.1: target locale id the translate-and-polish prompt should
+    /// produce (e.g. `"en"`, `"ja"`). Mirrored from `ProviderConfig`.
+    @Published public var translationTargetLocaleId: String = TranslationLanguageCatalog.defaultLocaleId
+    /// v0.2.1: effective predicate — translation is honoured only on
+    /// the cloud engine. The keyboard's chip / picker read this so the
+    /// UI can show a "需要云端" hint when the toggle is on while the
+    /// local engine is active.
+    public var isTranslationEffective: Bool {
+        translationEnabled && engineMode == "cloud"
+    }
 
     /// Convenience shorthand used by the pipeline and views.
     public var isLocalEngine: Bool { engineMode == "local" }
@@ -101,6 +115,12 @@ public final class KeyboardState: ObservableObject {
     public var setLocale:           (String) -> Void = { _ in }
     public var setEngineMode:        (String) -> Void = { _ in }
     public var setLocalASRBackend:  (LocalASRBackend) -> Void = { _ in }
+    /// v0.2.1: persist translation toggle. Wired in
+    /// `KeyboardViewController.installStateActions`.
+    public var setTranslationEnabled: (Bool) -> Void = { _ in }
+    /// v0.2.1: persist translation target locale id. Same wiring as
+    /// `setTranslationEnabled`.
+    public var setTranslationTargetLocaleId: (String) -> Void = { _ in }
     public var insertNewline:       () -> Void = {}
     public var insertSpace:         () -> Void = {}
     public var deleteBackward:      () -> Void = {}