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/Models/ProviderConfig.swift

@@ -39,6 +39,12 @@ public final class ProviderConfig: ObservableObject, @unchecked Sendable {
         // in the local engine. Default `false` — keeps the local engine
         // truly local unless the user explicitly opts in.
         static let localModeCloudPolishEnabled = "config.localModeCloudPolishEnabled"
+        // v0.2.1: optional translation step after ASR. When enabled, the
+        // post-ASR transcript is routed through the same LLM with a
+        // translate-and-polish prompt targeting `translationTargetLocaleId`.
+        // Mutually exclusive with the local-only promise — see `TranslationPolicy`.
+        static let translationEnabled = "config.translationEnabled"
+        static let translationTargetLocaleId = "config.translationTargetLocaleId"
     }
 
     @Published public var providerId: String {
@@ -115,6 +121,29 @@ public final class ProviderConfig: ObservableObject, @unchecked Sendable {
     @Published public var uiLanguage: AppUILanguage {
         didSet { defaults.set(uiLanguage.rawValue, forKey: Key.uiLanguage) }
     }
+    /// v0.2.1: whether to translate the transcript into
+    /// `translationTargetLocaleId` before insertion. Persisted in the App
+    /// Group so the keyboard extension can honour it (and so the chip on
+    /// the keyboard reflects the user's choice without a host-app round-
+    /// trip). Default `false` — translation is opt-in.
+    @Published public var translationEnabled: Bool {
+        didSet { defaults.set(translationEnabled, forKey: Key.translationEnabled) }
+    }
+    /// v0.2.1: BCP-47-ish target language id (e.g. `en`, `ja`, `ko`) the
+    /// translate-and-polish prompt should produce. Default `"en"`.
+    /// Persisted in the App Group for the same reason as `translationEnabled`.
+    @Published public var translationTargetLocaleId: String {
+        didSet { defaults.set(translationTargetLocaleId, forKey: Key.translationTargetLocaleId) }
+    }
+
+    /// v0.2.1: hard gate that decides whether the translation feature can
+    /// actually run. The keyboard honors `translationEnabled` only when
+    /// `engineMode == "cloud"` — the local engine is contractually ASR-
+    /// only, so translation is silently ignored (and the UI shows a hint)
+    /// even when the toggle is on.
+    public var isTranslationEffective: Bool {
+        translationEnabled && engineMode == "cloud"
+    }
 
     public var isConfigured: Bool {
         // Local engine (on-device ASR only) doesn't need an API key,
@@ -193,6 +222,15 @@ public final class ProviderConfig: ObservableObject, @unchecked Sendable {
         self.uiLanguage = AppUILanguage.fromStored(
             resolvedDefaults.string(forKey: Key.uiLanguage)
         )
+        // v0.2.1: translation toggle + target locale. Both default in a
+        // backwards-compatible way so existing installs keep their old
+        // behaviour (`false`/English) without prompting.
+        if resolvedDefaults.object(forKey: Key.translationEnabled) == nil {
+            self.translationEnabled = false
+        } else {
+            self.translationEnabled = resolvedDefaults.bool(forKey: Key.translationEnabled)
+        }
+        self.translationTargetLocaleId = resolvedDefaults.string(forKey: Key.translationTargetLocaleId) ?? "en"
 
         // Cloud no longer exposes off/transcribe; migrate legacy values.
         if self.engineMode == "cloud", self.modeId != "polish" {

OSGKeyboardShared/Models/TranslationLanguage.swift

@@ -0,0 +1,59 @@
+// TranslationLanguage.swift
+// OSGKeyboard · Shared
+//
+// Catalog of target languages the translation feature can produce.
+//
+// Kept deliberately small (~10 entries) to match the kind of choices
+// the user makes in the Settings picker / keyboard chip. We don't try
+// to expose every BCP-47 locale — the prompt just needs a target
+// language name, and a curated list reads better than a 100-row scroll.
+//
+// `id` is what gets persisted to the App Group. `promptLanguageName`
+// is the human-readable target name injected into the prompt (e.g.
+// the LLM sees "English", not "en"). `nativeName` is the endonym we
+// show in the picker UI ("日本語" instead of "Japanese").
+
+import Foundation
+
+public struct TranslationLanguage: Identifiable, Hashable, Sendable {
+    public let id: String
+    public let promptLanguageName: String
+    public let nativeName: String
+
+    public init(id: String, promptLanguageName: String, nativeName: String) {
+        self.id = id
+        self.promptLanguageName = promptLanguageName
+        self.nativeName = nativeName
+    }
+}
+
+public enum TranslationLanguageCatalog {
+    /// Default target language id used on fresh installs.
+    public static let defaultLocaleId = "en"
+
+    /// Curated set. Order matters — the picker / chip render top-to-
+    /// bottom, and `defaultLocaleId` is the default selection.
+    public static let all: [TranslationLanguage] = [
+        TranslationLanguage(id: "en",    promptLanguageName: "English",  nativeName: "English"),
+        TranslationLanguage(id: "zh-Hans", promptLanguageName: "Simplified Chinese", nativeName: "简体中文"),
+        TranslationLanguage(id: "zh-Hant", promptLanguageName: "Traditional Chinese", nativeName: "繁體中文"),
+        TranslationLanguage(id: "ja",    promptLanguageName: "Japanese", nativeName: "日本語"),
+        TranslationLanguage(id: "ko",    promptLanguageName: "Korean",   nativeName: "한국어"),
+        TranslationLanguage(id: "fr",    promptLanguageName: "French",   nativeName: "Français"),
+        TranslationLanguage(id: "de",    promptLanguageName: "German",   nativeName: "Deutsch"),
+        TranslationLanguage(id: "es",    promptLanguageName: "Spanish",  nativeName: "Español"),
+        TranslationLanguage(id: "ru",    promptLanguageName: "Russian",  nativeName: "Русский"),
+        TranslationLanguage(id: "pt",    promptLanguageName: "Portuguese", nativeName: "Português"),
+    ]
+
+    /// Resolve a stored locale id to its catalog entry. Falls back to
+    /// `defaultLocaleId` when the id is missing or unknown — matches the
+    /// pattern used elsewhere (e.g. `ASRLocaleLabels`) so the keyboard
+    /// never crashes on a stale persisted value.
+    public static func resolve(_ id: String) -> TranslationLanguage {
+        if let match = all.first(where: { $0.id == id }) {
+            return match
+        }
+        return all.first { $0.id == defaultLocaleId } ?? all[0]
+    }
+}