{
    "title": "chat_attachments",
    "type": "object",
    "properties": {
        "id": {
            "type": "integer",
            "description": "Primary key, auto-increment"
        },
        "conversation_id": {
            "type": "integer",
            "description": "FK to chat_conversations.id"
        },
        "message_id": {
            "type": "integer",
            "description": "FK to chat_messages.id"
        },
        "object_key": {
            "type": "string",
            "description": "Object key in storage bucket"
        },
        "file_name": {
            "type": "string",
            "description": "Original filename"
        },
        "mime_type": {
            "type": "string",
            "description": "File MIME type"
        },
        "size_bytes": {
            "type": "integer",
            "description": "File size in bytes"
        },
        "url": {
            "type": "string",
            "description": "Public URL of the file"
        }
    },
    "required": [
        "id",
        "conversation_id",
        "object_key",
        "file_name"
    ]
}