Add managed Linux graphics and environment profiles

[SaicharanKandukuri]

• Adds selectable software, Zink, VirGL, VirGL ANGLE, and experimental Venus profiles.
• Shows only profiles supported by the device and installed Linux drivers, with a runtime guard for saved settings.
• Applies graphics and environment settings automatically to terminals, apps, and desktops.
• Bundles the verified Venus host runtime and Mesa 26.1.5 for Ubuntu 22.04 and 24.04 without replacing distro packages.
• Adds editable per-system variables, resettable uDroid defaults, compatibility mounts, and private shared memory.
• Passes unit tests, asset verification, lint, and the dev APK build; verified on Pixel with Ubuntu 24.04.
• Stacked on Add desktop mouse controls and process guidance #27; merge Add desktop mouse controls and process guidance #27 first.