Fix #9: Validate sender exists and is active in WS chat.send

src/tracker/ws/handler.py

@@ -295,9 +295,10 @@ async def _handle_chat_send(session_id: str, data: dict):
         return
 
     async with async_session() as db:
-        result = await db.execute(select(Member).where(Member.slug == slug))
+        result = await db.execute(select(Member).where(Member.slug == slug, Member.is_active == True))
         member = result.scalar_one_or_none()
         if not member:
+            await client.ws.send_json({"type": WSEventType.ERROR, "message": "Member not found or inactive"})
             return
 
         msg = Message(