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).

OSGKeyboardExt/zh-Hans.lproj/Keyboard.strings

@@ -177,6 +177,15 @@
 "locale.chip.ja-JP" = "日";
 "locale.chip.ko-KR" = "韩";
 
+/* 翻译 chip (v0.2.1) */
+"keyboard.translation.off" = "翻译";
+"keyboard.translation.enable" = "开启翻译";
+"keyboard.translation.disable" = "关闭翻译";
+"keyboard.translation.needsCloudShort" = "需云端";
+"keyboard.translation.a11y" = "翻译";
+"keyboard.translation.a11yHint" = "切换翻译开关或修改目标语言。";
+"keyboard.error.translation.needsCloud" = "翻译需要云端引擎，请到设置切换为云端模式。";
+
 /* Mode chip labels */
 "mode.off" = "关闭";
 "mode.transcribe" = "转写";