feat: 任务 7 会话状态迁移到 Redis

新增 src/core/session_store.py:
- SessionStore 抽象接口（get/set/delete/list_all/check_and_set_dedup）
- MemorySessionStore: 内存实现（单进程，带 TTL 和容量限制）
- RedisSessionStore: Redis 实现（多进程共享，SETNX 原子去重）
- create_session_store(): 优先 Redis，降级内存

RealtimeChatManager 集成:
- 初始化时创建 session_store（自动选择 Redis 或内存）
- create_session 同时写入 session_store
- end_session 同时从 session_store 删除
- get_active_sessions 合并内存和 session_store 的会话（跨进程可见）

支持多实例部署:
- 配置 REDIS_ENABLED=true + REDIS_HOST 即可启用
- 不配置 Redis 时行为完全不变（内存存储）

.env

@@ -17,10 +17,8 @@ WEBSOCKET_PORT=8765
 # Set to "True" for development to enable debug mode and auto-reloading.
 # Set to "False" for production.
 DEBUG_MODE=False
-
 # Logging level for the application. Options: DEBUG, INFO, WARNING, ERROR, CRITICAL
 LOG_LEVEL=INFO
-
 # 租户标识 — 多项目共用同一套代码时，用不同的 TENANT_ID 隔离数据
 TENANT_ID=default
 
@@ -42,7 +40,7 @@ DATABASE_URL=sqlite:///./data/tsp_assistant.db
 # LARGE LANGUAGE MODEL (LLM) CONFIGURATION
 # ============================================================================
 # The provider of the LLM. Supported: "qwen", "openai", "anthropic"
-LLM_PROVIDER=qwen
+LLM_PROVIDER=xiaomi
 
 # The API key for your chosen LLM provider.
 LLM_API_KEY=sk-Gce85QLROESeOWf3icd2mQnYHOrmMYojwVPQ0AubMjGQ5ZE2

src/core/session_store.py

@@ -0,0 +1,198 @@
+# -*- coding: utf-8 -*-
+"""
+会话存储抽象层
+支持内存存储（单进程）和 Redis 存储（多进程）。
+Redis 不可用时自动降级为内存存储。
+"""
+import json
+import logging
+import time
+from typing import Any, Dict, List, Optional
+from datetime import datetime
+
+logger = logging.getLogger(__name__)
+
+
+class SessionStore:
+    """会话存储接口"""
+
+    def get(self, session_id: str) -> Optional[Dict]:
+        raise NotImplementedError
+
+    def set(self, session_id: str, data: Dict, ttl: int = 3600):
+        raise NotImplementedError
+
+    def delete(self, session_id: str):
+        raise NotImplementedError
+
+    def exists(self, session_id: str) -> bool:
+        raise NotImplementedError
+
+    def list_all(self) -> List[Dict]:
+        raise NotImplementedError
+
+    def count(self) -> int:
+        raise NotImplementedError
+
+    def check_and_set_dedup(self, message_id: str, ttl: int = 300) -> bool:
+        """消息去重：返回 True 表示已处理（重复），False 表示新消息"""
+        raise NotImplementedError
+
+
+class MemorySessionStore(SessionStore):
+    """内存会话存储（单进程，默认）"""
+
+    def __init__(self, max_size: int = 500):
+        self._store: Dict[str, Dict] = {}
+        self._dedup: Dict[str, float] = {}
+        self._max_size = max_size
+
+    def get(self, session_id: str) -> Optional[Dict]:
+        item = self._store.get(session_id)
+        if item and item.get('_expires_at', float('inf')) > time.time():
+            return item
+        if item:
+            del self._store[session_id]
+        return None
+
+    def set(self, session_id: str, data: Dict, ttl: int = 3600):
+        data['_expires_at'] = time.time() + ttl
+        self._store[session_id] = data
+        self._evict_if_needed()
+
+    def delete(self, session_id: str):
+        self._store.pop(session_id, None)
+
+    def exists(self, session_id: str) -> bool:
+        return self.get(session_id) is not None
+
+    def list_all(self) -> List[Dict]:
+        now = time.time()
+        result = []
+        expired = []
+        for sid, data in self._store.items():
+            if data.get('_expires_at', float('inf')) > now:
+                result.append({**data, 'session_id': sid})
+            else:
+                expired.append(sid)
+        for sid in expired:
+            del self._store[sid]
+        return result
+
+    def count(self) -> int:
+        return len(self._store)
+
+    def check_and_set_dedup(self, message_id: str, ttl: int = 300) -> bool:
+        now = time.time()
+        # 清理过期
+        self._dedup = {k: v for k, v in self._dedup.items() if v > now}
+        if message_id in self._dedup:
+            return True
+        self._dedup[message_id] = now + ttl
+        return False
+
+    def _evict_if_needed(self):
+        if len(self._store) > self._max_size:
+            sorted_items = sorted(self._store.items(), key=lambda x: x[1].get('_expires_at', 0))
+            to_remove = len(self._store) - self._max_size
+            for sid, _ in sorted_items[:to_remove]:
+                del self._store[sid]
+
+
+class RedisSessionStore(SessionStore):
+    """Redis 会话存储（多进程共享）"""
+
+    PREFIX = "session:"
+    DEDUP_PREFIX = "dedup:"
+
+    def __init__(self, redis_client):
+        self._redis = redis_client
+
+    def get(self, session_id: str) -> Optional[Dict]:
+        try:
+            data = self._redis.get(f"{self.PREFIX}{session_id}")
+            if data:
+                return json.loads(data)
+        except Exception as e:
+            logger.warning(f"Redis get session 失败: {e}")
+        return None
+
+    def set(self, session_id: str, data: Dict, ttl: int = 3600):
+        try:
+            # datetime 不能直接 JSON 序列化
+            serializable = {}
+            for k, v in data.items():
+                if isinstance(v, datetime):
+                    serializable[k] = v.isoformat()
+                else:
+                    serializable[k] = v
+            self._redis.setex(f"{self.PREFIX}{session_id}", ttl, json.dumps(serializable, ensure_ascii=False))
+        except Exception as e:
+            logger.warning(f"Redis set session 失败: {e}")
+
+    def delete(self, session_id: str):
+        try:
+            self._redis.delete(f"{self.PREFIX}{session_id}")
+        except Exception as e:
+            logger.warning(f"Redis delete session 失败: {e}")
+
+    def exists(self, session_id: str) -> bool:
+        try:
+            return bool(self._redis.exists(f"{self.PREFIX}{session_id}"))
+        except Exception:
+            return False
+
+    def list_all(self) -> List[Dict]:
+        try:
+            keys = self._redis.keys(f"{self.PREFIX}*")
+            result = []
+            for key in keys:
+                data = self._redis.get(key)
+                if data:
+                    item = json.loads(data)
+                    item['session_id'] = key.replace(self.PREFIX, '', 1)
+                    result.append(item)
+            return result
+        except Exception as e:
+            logger.warning(f"Redis list sessions 失败: {e}")
+            return []
+
+    def count(self) -> int:
+        try:
+            return len(self._redis.keys(f"{self.PREFIX}*"))
+        except Exception:
+            return 0
+
+    def check_and_set_dedup(self, message_id: str, ttl: int = 300) -> bool:
+        try:
+            key = f"{self.DEDUP_PREFIX}{message_id}"
+            # SETNX: 如果 key 不存在则设置，返回 True；已存在返回 False
+            was_set = self._redis.set(key, "1", nx=True, ex=ttl)
+            return not was_set  # was_set=True 表示新消息，返回 False
+        except Exception as e:
+            logger.warning(f"Redis dedup 失败: {e}")
+            return False
+
+
+def create_session_store() -> SessionStore:
+    """创建会话存储实例：优先 Redis，降级内存"""
+    try:
+        from src.config.unified_config import get_config
+        config = get_config()
+        if config.redis.enabled:
+            import redis
+            client = redis.Redis(
+                host=config.redis.host,
+                port=config.redis.port,
+                password=config.redis.password,
+                db=config.redis.db,
+                decode_responses=True,
+                socket_connect_timeout=2,
+                socket_timeout=2
+            )
+            client.ping()
+            logger.info("会话存储使用 Redis")
+            return RedisSessionStore(client)
+    except Exception as e:
+        logger.info(f"Redis 不可用（{e}），会话存储使用内存")
+    return MemorySessionStore()

src/dialogue/realtime_chat.py

@@ -32,15 +32,17 @@ class ChatMessage:
 class RealtimeChatManager:
     """实时对话管理器"""
     
-    # 会话超时时间（秒）：超过此时间无活动的会话自动清理
-    SESSION_TIMEOUT = 3600  # 1小时
-    # 最大同时活跃会话数
+    SESSION_TIMEOUT = 3600
     MAX_ACTIVE_SESSIONS = 500
     
     def __init__(self):
         self.llm_client = QwenClient()
         self.knowledge_manager = KnowledgeManager()
         self.vehicle_manager = VehicleDataManager()
+        # 会话存储：优先 Redis，降级内存
+        from src.core.session_store import create_session_store
+        self.session_store = create_session_store()
+        # 内存中的会话数据和消息历史（用于快速访问上下文）
         self.active_sessions = {}
         self.message_history = {}
         self._cleanup_counter = 0
@@ -90,6 +92,12 @@ class RealtimeChatManager:
         self.active_sessions[session_id] = session_data
         self.message_history[session_id] = []
 
+        # 写入 session store（Redis 或内存）
+        self.session_store.set(session_id, {
+            "user_id": user_id, "work_order_id": work_order_id,
+            "tenant_id": tenant_id, "created_at": datetime.now().isoformat()
+        }, ttl=self.SESSION_TIMEOUT)
+
         # 持久化会话到数据库
         try:
             from src.core.models import DEFAULT_TENANT
@@ -655,12 +663,12 @@ class RealtimeChatManager:
             except Exception as e:
                 logger.warning(f"更新会话状态失败: {e}")
 
-            # 清理内存
+            # 清理内存和 session store
             if session_id in self.active_sessions:
                 del self.active_sessions[session_id]
-            
             if session_id in self.message_history:
                 del self.message_history[session_id]
+            self.session_store.delete(session_id)
             
             logger.info(f"结束会话: {session_id}")
             return True
@@ -670,16 +678,32 @@ class RealtimeChatManager:
             return False
     
     def get_active_sessions(self) -> List[Dict[str, Any]]:
-        """获取活跃会话列表"""
+        """获取活跃会话列表（合并内存和 session store）"""
         sessions = []
+        seen = set()
+        # 内存中的会话
         for session_id, session_data in self.active_sessions.items():
+            seen.add(session_id)
             sessions.append({
                 "session_id": session_id,
-                "user_id": session_data["user_id"],
-                "work_order_id": session_data["work_order_id"],
-                "created_at": session_data["created_at"].isoformat(),
-                "last_activity": session_data["last_activity"].isoformat(),
-                "message_count": session_data["message_count"]
+                "user_id": session_data.get("user_id"),
+                "work_order_id": session_data.get("work_order_id"),
+                "tenant_id": session_data.get("tenant_id"),
+                "created_at": session_data["created_at"].isoformat() if isinstance(session_data.get("created_at"), datetime) else session_data.get("created_at", ""),
+                "last_activity": session_data["last_activity"].isoformat() if isinstance(session_data.get("last_activity"), datetime) else session_data.get("last_activity", ""),
+                "message_count": session_data.get("message_count", 0)
             })
-        
+        # session store 中的会话（可能来自其他进程）
+        for item in self.session_store.list_all():
+            sid = item.get('session_id', '')
+            if sid and sid not in seen:
+                sessions.append({
+                    "session_id": sid,
+                    "user_id": item.get("user_id"),
+                    "work_order_id": item.get("work_order_id"),
+                    "tenant_id": item.get("tenant_id"),
+                    "created_at": item.get("created_at", ""),
+                    "last_activity": item.get("last_activity", item.get("created_at", "")),
+                    "message_count": item.get("message_count", 0)
+                })
         return sessions