Adopt package: update Maintainer and close WNPP bug #921622 (0.4.2-4)

This Merge Request completes the adoption and modernization of the libvisual package, as requested in WNPP bug #921622 and in the review feedback from Tobias Frost on RFS bug #1121907.

Changes included:

Packaging updates

• Set myself as Maintainer and perform minor control-file cleanups.
• Update German translation from bug #1055631.
• Introduce optional build profile pkg.libvisual.nosdl to break the historic libvisual ↔️ libsdl1.2 bootstrap cycle. (Closes: #1077534) The dependency cycle no longer appears in the archive, but keeping this profile ensures future bootstrappability.
• When the nosdl profile is active, lv-tool and examples are disabled.

Notes on lv-tool and SDL1.2

• lv-tool is the only component requiring SDL 1.2.
• The SDL 1.2 deprecation and the transition toward sdl12-compat remain tracked in bug #1038102. This MR does not attempt a port to SDL2.

Next steps

After opening this MR, I will send a follow-up to RFS bug #1121907, removing the moreinfo tag and pointing to this MR for the next review step.