Merge remote-tracking branch 'origin/feature/7096-integrate-the-new-logo-in-about-tails' into stable

Conflicts:
	wiki/src/doc/first_steps.index.fr.po
	wiki/src/doc/first_steps/bug_reporting/tails_does_not_start.fr.po
	wiki/src/doc/first_steps/start_tails.fr.po
	wiki/src/doc/first_steps/startup_options/mac_spoofing.fr.po
	wiki/src/download.de.po
	wiki/src/download.fr.po

Conflicts:
	wiki/src/doc/encryption_and_privacy/gpgapplet/decrypt_verify.de.po
	wiki/src/doc/encryption_and_privacy/gpgapplet/public-key_cryptography.de.po

Conflicts:
	wiki/src/doc/encryption_and_privacy/gpgapplet/public-key_cryptography.fr.po

Closes #7054.

For some reason, the splash screen appears much darker in syslinux than the
original image is, either in full colors, either in 65536 colors. Adding more
contrast solves this.