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/AppGroupStore.swift

@@ -39,6 +39,9 @@ public struct AppGroupStore: @unchecked Sendable {
         static let uiLanguage       = "config.uiLanguage"
         // v0.2.0: opt-in cloud polish step after local-mode ASR.
         static let localModeCloudPolishEnabled = "config.localModeCloudPolishEnabled"
+        // v0.2.1: translation toggle + target locale id (e.g. "en").
+        static let translationEnabled = "config.translationEnabled"
+        static let translationTargetLocaleId = "config.translationTargetLocaleId"
     }
 
     // MARK: - Reads
@@ -104,6 +107,22 @@ public struct AppGroupStore: @unchecked Sendable {
         AppUILanguage.fromStored(defaults.string(forKey: Key.uiLanguage))
     }
 
+    /// v0.2.1: whether the keyboard should translate the post-ASR transcript
+    /// before inserting it. Honored only when `engineMode == "cloud"` — see
+    /// `ProviderConfig.isTranslationEffective` for the effective predicate.
+    public var translationEnabled: Bool {
+        guard defaults.object(forKey: Key.translationEnabled) != nil else {
+            return false
+        }
+        return defaults.bool(forKey: Key.translationEnabled)
+    }
+
+    /// v0.2.1: target locale id the translate-and-polish prompt should
+    /// produce (e.g. `"en"`). Defaults to `"en"` when nothing is stored.
+    public var translationTargetLocaleId: String {
+        defaults.string(forKey: Key.translationTargetLocaleId) ?? "en"
+    }
+
     // MARK: - Writes
 
     public func setModeId(_ id: String) {
@@ -126,6 +145,19 @@ public struct AppGroupStore: @unchecked Sendable {
         defaults.set(language.rawValue, forKey: Key.uiLanguage)
     }
 
+    /// v0.2.1: persist translation toggle. The keyboard extension reads
+    /// this on every `load()` and `refreshRuntimeFlags()` so the chip
+    /// reflects the latest value without a host-app round-trip.
+    public func setTranslationEnabled(_ enabled: Bool) {
+        defaults.set(enabled, forKey: Key.translationEnabled)
+    }
+
+    /// v0.2.1: persist target locale id (e.g. `"en"`, `"ja"`). Same
+    /// read cadence as `setTranslationEnabled`.
+    public func setTranslationTargetLocaleId(_ id: String) {
+        defaults.set(id, forKey: Key.translationTargetLocaleId)
+    }
+
     // MARK: - Client
 
     public func makeClient() -> LLMClient {