muster release v5.23.3

The release binaries report their release tag again. muster version on the v5.22.0 binary printed v1.12.1-0.20260915144925-e6c760a32b48: the CI build stamped the commit and the build time but no version, so the binary fell back to the version Go’s own VCS stamping had derived – and as the module path is github.com/giantswarm/muster with no /v5 suffix, Go only considers v0 and v1 tags and turned every v5 release commit into a pseudo-version of the last v1 tag. Because that version is older than every release, muster self-update re-installed the very release it was running on each time instead of reporting “Current version is the latest.” The build now links the tag into the binary (make stamp-version, run by make test between the architect orb writing its link flags and linking with them; a branch build gets git describe, e.g. v5.23.2-1-g4be8379e), a pseudo-version from the build info is no longer shown as the version, and self-update refuses a version that is not a release (dev, a bare commit) instead of panicking on it. (#1256)