remove：移除无用代码

src/common/database/database_model.py

@@ -306,8 +306,6 @@ class Expression(BaseModel):
     # new mode fields
     context = TextField(null=True)
     context_words = TextField(null=True)
-    full_context = TextField(null=True)
-    full_context_embedding = TextField(null=True)
 
     last_active_time = FloatField()
     chat_id = TextField(index=True)
@@ -324,6 +322,7 @@ class MemoryChest(BaseModel):
 
     title = TextField()  # 标题
     content = TextField()  # 内容
+    locked = BooleanField(default=False)  # 是否锁定
 
     class Meta:
         table_name = "memory_chest"