feat(i18n): persist language preference and thread through chat, memoir, TTS

- Add users.language_preference (Alembic 0018, default zh); capture at signup/SMS
  only; expose on auth and profile APIs
- Lite English prompts for chat and memoir; localized stage labels and agent
  names (Life Echo / 岁月知己)
- Tencent TTS: language-aware synthesis, ModelType=1 for 501004, English chunking
- WebSocket pipeline: emit all AGENT_RESPONSE segments when TTS cancels; INFO logs
  for tts_this_turn and TTS decisions; on-demand TTS logging
- Expo: device language on auth, i18n tiers/agent name, [SPLIT] streaming UX fixes
- Tests for migration, prompts, pipeline, router tts_this_turn, reply segments

Co-authored-by: Cursor <cursoragent@cursor.com>

api/app/agents/chat/orchestrator.py

@@ -51,9 +51,20 @@ if TYPE_CHECKING:
 
 logger = get_logger(__name__)
 
-_UNAUTH_TURN = AgentChatTurn(
+_UNAUTH_TURN_ZH = AgentChatTurn(
     messages=["暂时没法继续对话，请先登录后再试。"], skip_tts=True
 )
+_UNAUTH_TURN_EN = AgentChatTurn(
+    messages=["You'll need to sign in again before we can continue."],
+    skip_tts=True,
+)
+
+
+def _user_language(user: Optional["User"]) -> str:
+    if not user:
+        return "zh"
+    lang = getattr(user, "language_preference", None) or "zh"
+    return "en" if str(lang).lower() == "en" else "zh"
 
 
 async def _fetch_interview_memory_bundle(
@@ -145,6 +156,7 @@ class ChatOrchestrator:
         根据 missing_fields 路由到 ProfileAgent 或 InterviewAgent。
         """
         t0 = time.perf_counter()
+        language = _user_language(user)
 
         # --- 资料收集模式 ---
         if user:
@@ -179,7 +191,10 @@ class ChatOrchestrator:
                         # Profile 阶段每轮都抽取：短确认语也可能带可推断资料，跳过抽取会导致槽位长期不更新
                         extracted = (
                             await self.profile_agent.extract_profile_from_message(
-                                user_message, missing, conversation_id=conversation_id
+                                user_message,
+                                missing,
+                                conversation_id=conversation_id,
+                                language=language,
                             )
                         )
                         logger.info(
@@ -198,7 +213,7 @@ class ChatOrchestrator:
                         if not remaining:
                             st = await get_or_create_state(user.id, db)
                             interview_stage_hint = life_stage_display_name(
-                                st.current_stage
+                                st.current_stage, language=language
                             )
                         responses = await self.profile_agent.generate_profile_followup(
                             conversation_id=conversation_id,
@@ -207,6 +222,7 @@ class ChatOrchestrator:
                             filled_fields=filled,
                             nickname=user.nickname or "",
                             interview_stage_hint=interview_stage_hint,
+                            language=language,
                         )
                         if agent_summary_enabled():
                             logger.info(
@@ -223,8 +239,13 @@ class ChatOrchestrator:
                         )
                     except Exception as e:
                         logger.exception("资料收集处理失败: {}", e)
+                        fb_msg = (
+                            "Sorry, I missed that. Could you say it again?"
+                            if language == "en"
+                            else "不好意思刚才没接住，你再说一遍好吗？"
+                        )
                         return AgentChatTurn(
-                            messages=["不好意思刚才没接住，你再说一遍好吗？"],
+                            messages=[fb_msg],
                             skip_tts=False,
                             memory_retrieval_trace=None,
                         )
@@ -239,7 +260,7 @@ class ChatOrchestrator:
                     (time.perf_counter() - t0) * 1000,
                     conversation_id,
                 )
-            return _UNAUTH_TURN
+            return _UNAUTH_TURN_EN if language == "en" else _UNAUTH_TURN_ZH
 
         log_agent_detail(
             logger,
@@ -284,6 +305,7 @@ class ChatOrchestrator:
                 birth_place=user.birth_place,
                 grew_up_place=user.grew_up_place,
                 occupation=user.occupation,
+                language=language,
             )
             background_voice = infer_background_voice(user.occupation)
             occupation = user.occupation or ""
@@ -331,6 +353,7 @@ class ChatOrchestrator:
             profile_era_place=profile_era_place,
             stage_switched_this_turn=stage_switched_this_turn,
             scene_cues_for_planner=scene_cues_for_planner,
+            language=language,
         )
         recent_questions = prompt_state.recent_questions
         if turn.interview_state_meta and isinstance(turn.interview_state_meta, dict):
@@ -387,6 +410,7 @@ class ChatOrchestrator:
         voice_session_id: str | None = None,
         user_message_timestamp: datetime | None = None,
         audio_duration_seconds: int | None = None,
+        language: str = "zh",
     ) -> List[str]:
         """委托 ProfileAgent 生成资料追问（持久化由调用方负责）。"""
         return await self.profile_agent.generate_profile_followup(
@@ -395,6 +419,7 @@ class ChatOrchestrator:
             missing_fields=missing_fields,
             filled_fields=filled_fields,
             nickname=nickname,
+            language=language,
         )
 
     async def generate_profile_greeting(
@@ -402,12 +427,14 @@ class ChatOrchestrator:
         conversation_id: str,
         missing_fields: List[str],
         nickname: str = "",
+        language: str = "zh",
     ) -> List[str]:
         """委托 ProfileAgent 生成资料收集开场白（持久化由调用方负责）。"""
         return await self.profile_agent.generate_profile_greeting(
             conversation_id=conversation_id,
             missing_fields=missing_fields,
             nickname=nickname,
+            language=language,
         )
 
     async def generate_response_with_state(
@@ -431,6 +458,7 @@ class ChatOrchestrator:
         profile_era_place: str = "",
         stage_switched_this_turn: bool = False,
         scene_cues_for_planner: Optional[list[str]] = None,
+        language: str = "zh",
     ) -> AgentChatTurn:
         """委托 InterviewAgent 生成访谈回复（持久化由调用方负责）。"""
         return await self.interview_agent.generate_response_with_state(
@@ -449,6 +477,7 @@ class ChatOrchestrator:
             profile_era_place=profile_era_place,
             stage_switched_this_turn=stage_switched_this_turn,
             scene_cues_for_planner=scene_cues_for_planner,
+            language=language,
         )
 
     def detect_user_stage(self, user_message: str) -> str:
@@ -464,6 +493,7 @@ class ChatOrchestrator:
         occupation: str = "",
         profile_birth_year: Optional[int] = None,
         profile_era_place: str = "",
+        language: str = "zh",
     ) -> List[str]:
         """
         委托 InterviewAgent 生成访谈开场白（持久化由调用方 ConversationHistoryStore 负责）。
@@ -476,4 +506,5 @@ class ChatOrchestrator:
             occupation=occupation,
             profile_birth_year=profile_birth_year,
             profile_era_place=profile_era_place,
+            language=language,
         )