CREATE TABLE IF NOT EXISTS wa_internal_notes (
    id BIGINT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
    conversation_id BIGINT UNSIGNED NOT NULL,
    agent_id BIGINT UNSIGNED NOT NULL,
    note TEXT NOT NULL,
    created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
    KEY idx_note_conversation (conversation_id, id),
    CONSTRAINT fk_note_conversation FOREIGN KEY (conversation_id) REFERENCES wa_conversations(id) ON DELETE CASCADE,
    CONSTRAINT fk_note_agent FOREIGN KEY (agent_id) REFERENCES wa_agents(id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;