fix: 用户隔离完整性 + 聊天去重

1. 启动时不加载历史消息（等第一条消息确定身份后按需恢复）
2. MemoryStore 改为 HashMap<user_id, Vec<mem>>，按用户隔离缓存
3. session.current_user_id 与外部 mutex 同步
4. chat_records.message_id 加 UNIQUE 索引 + ON CONFLICT DO NOTHING

src/context/tools.rs

@@ -1,22 +1,22 @@
 use sqlx::PgPool;
+use std::collections::HashMap;
 use std::sync::Arc;
 use tokio::sync::Mutex;
 
-/// 长期记忆管理器（内存 + PostgreSQL 双写）
+/// 长期记忆管理器（内存 + PostgreSQL 双写，按用户隔离）
 pub struct MemoryStore {
     pool: Option<Arc<PgPool>>,
-    cache: Arc<Mutex<Vec<String>>>,
+    cache: Arc<Mutex<HashMap<String, Vec<String>>>>,
 }
 
 impl MemoryStore {
     pub fn new(pool: Option<Arc<PgPool>>) -> Self {
         Self {
             pool,
-            cache: Arc::new(Mutex::new(Vec::new())),
+            cache: Arc::new(Mutex::new(HashMap::new())),
         }
     }
 
-    /// 从数据库加载记忆到缓存
     pub async fn load(&self, user_id: &str) {
         let pool = match self.pool.as_ref() {
             Some(p) => p.clone(),
@@ -30,37 +30,32 @@ impl MemoryStore {
         .fetch_all(pool.as_ref())
         .await
         {
-            let mut cache = self.cache.lock().await;
-            *cache = rows.into_iter().map(|(c,)| c).collect();
+            let mems: Vec<String> = rows.into_iter().map(|(c,)| c).collect();
+            self.cache.lock().await.insert(uid.to_string(), mems);
         }
     }
 
-    /// 读取记忆
-    pub async fn read(&self) -> String {
-        let mems = self.cache.lock().await;
-        if mems.is_empty() { "暂无长期记忆".to_string() } else {
-            mems.iter().enumerate().map(|(i, m)| format!("{}. {}", i+1, m)).collect::<Vec<_>>().join("\n")
-        }
-    }
-
-    /// 按用户读取记忆（缓存按 user_id 过滤由调用方保证，这里简化为全量读取）
-    pub async fn read_for(&self, _user_id: &str) -> String { self.read().await }
-
-    /// 写入记忆
-    pub async fn write(&self, content: &str) -> String { self.write_for("default", content).await }
-
-    /// 按用户写入
-    pub async fn write_for(&self, user_id: &str, content: &str) -> String {
-        self.cache.lock().await.push(content.to_string());
+    pub async fn read_for(&self, user_id: &str) -> String {
         let uid = if user_id.is_empty() { "default" } else { user_id };
+        let cache = self.cache.lock().await;
+        match cache.get(uid) {
+            Some(m) if !m.is_empty() => m.iter().enumerate()
+                .map(|(i, v)| format!("{}. {}", i + 1, v))
+                .collect::<Vec<_>>()
+                .join("\n"),
+            _ => "暂无长期记忆".to_string(),
+        }
+    }
+
+    pub async fn write_for(&self, user_id: &str, content: &str) -> String {
+        let uid = if user_id.is_empty() { "default" } else { user_id };
+        self.cache.lock().await.entry(uid.to_string()).or_default().push(content.to_string());
         if let Some(ref pool) = self.pool {
-            let _ = sqlx::query(
-                "INSERT INTO user_memories (user_id, content) VALUES ($1, $2)",
-            )
-            .bind(uid)
-            .bind(content)
-            .execute(pool.as_ref())
-            .await;
+            let _ = sqlx::query("INSERT INTO user_memories (user_id, content) VALUES ($1, $2)")
+                .bind(uid)
+                .bind(content)
+                .execute(pool.as_ref())
+                .await;
         }
         "已添加长期记忆".to_string()
     }
@@ -73,7 +68,6 @@ pub async fn read_summaries(
     let s = session.lock().await;
     let mut lines: Vec<String> = Vec::new();
 
-    // 内存中的摘要
     for sum in &s.summaries {
         let reason = match sum.reason {
             super::types::SummaryReason::Overflow => "上下文压缩",
@@ -87,7 +81,6 @@ pub async fn read_summaries(
         ));
     }
 
-    // 数据库中的历史摘要
     if let Some(pool) = &s.db_pool {
         if let Ok(db_summaries) = crate::db::models::load_summaries(pool, 5).await {
             for text in db_summaries {
@@ -98,9 +91,5 @@ pub async fn read_summaries(
         }
     }
 
-    if lines.is_empty() {
-        "暂无历史摘要".to_string()
-    } else {
-        lines.join("\n---\n")
-    }
+    if lines.is_empty() { "暂无历史摘要".to_string() } else { lines.join("\n---\n") }
 }