www/tor-browser: Improve port

- Improve "fix build on i386" - use www/node24 for i386 only.
- Unification of Makefile with Firefox - make it more similar.
- Use ${DESKTOPDIR} instead of ${PREFIX}/share/applications.
- Reduce the number of mkdir calls.

PR:		288108
Approved by:	Martin Filla <freebsd@sysctl.cz> (maintainer)
MFH:		2025Q3