feat: add NVIDIA and AMD (Mesa Rusticl/OpenCL) GPU variants, bump to 1.5.2.1-beta.4

[remcoros]

Summary

Adds GPU variant support and bumps the package to v1.5.2:0-beta.4.

Variants

Variant	Image	Arch	Hardware requirement
generic	frigate-docker:1.5.2.1	x86_64 + aarch64	none
nvidia	frigate-docker:1.5.2.1	x86_64	driver: nvidia
amd	frigate-docker:1.5.2.1-amd	x86_64	driver: amdgpu

• generic — CPU, Intel OpenCL (bundled in Docker image on amd64), NVIDIA (via nvidiaContainer on nvidia variant)
• nvidia — same image, nvidiaContainer: true, hardware-matched to NVIDIA GPU
• amd — separate -amd image using Mesa Rusticl/radeonsi OpenCL; no ROCm required

Also

• Adopts startos/versions/current.ts version file structure
• Bumps version to 1.5.2:0-beta.4 / Docker image 1.5.2.1

Depends on

• Docker image PR: feat: add AMD GPU image variant frigate-docker#6 (must be merged and 1.5.2.1 + 1.5.2.1-amd tags published before this package can be installed)