CREATE TABLE IF NOT EXISTS account_invitations (
  id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
  company_id INT UNSIGNED NOT NULL,
  user_id INT UNSIGNED NOT NULL,
  invited_by INT UNSIGNED NULL,
  token_hash CHAR(64) NOT NULL,
  status ENUM('pending','accepted','revoked') NOT NULL DEFAULT 'pending',
  expires_at DATETIME NOT NULL,
  accepted_at DATETIME NULL,
  created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
  updated_at DATETIME NULL ON UPDATE CURRENT_TIMESTAMP,
  UNIQUE KEY uniq_account_invitation_hash (token_hash),
  INDEX idx_account_invitation_user (company_id, user_id, status)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;