Fix D-Bus activation race with PAM-launched ksecretd
When xdg-desktop-portal triggers D-Bus activation of ksecretd early in login, it races with the PAM-launched instance that has the password hash. If D-Bus wins, auto-unlock fails and users get prompted.
Add detection for D-Bus activation: if --pam-login argument is NOT present and PAM kwallet integration IS configured, wait up to 5 seconds for the PAM instance to register on D-Bus first.
Note: Only check for --pam-login argument, not PAM_KWALLET5_LOGIN env var. The env var propagates to all session processes including D-Bus activated ones, making it unreliable.