Add ChatSessionState model

surfsense_backend/app/db.py

@@ -472,6 +472,38 @@ class ChatCommentMention(BaseModel, TimestampMixin):
     mentioned_user = relationship("User")
 
 
+class ChatSessionState(BaseModel):
+    """
+    Tracks real-time session state for shared chat collaboration.
+    One record per thread, synced via Electric SQL.
+    """
+
+    __tablename__ = "chat_session_state"
+
+    thread_id = Column(
+        Integer,
+        ForeignKey("new_chat_threads.id", ondelete="CASCADE"),
+        nullable=False,
+        unique=True,
+        index=True,
+    )
+    ai_responding_to_user_id = Column(
+        UUID(as_uuid=True),
+        ForeignKey("user.id", ondelete="SET NULL"),
+        nullable=True,
+        index=True,
+    )
+    updated_at = Column(
+        TIMESTAMP(timezone=True),
+        nullable=False,
+        default=lambda: datetime.now(UTC),
+        onupdate=lambda: datetime.now(UTC),
+    )
+
+    thread = relationship("NewChatThread")
+    ai_responding_to_user = relationship("User")
+
+
 class Document(BaseModel, TimestampMixin):
     __tablename__ = "documents"