feat: bump stable-diffusion-cpp to 2026-03-01#5 for ESRGAN upscaler APIs

[gabrielgrigoras-serv]

Summary

Bump stable-diffusion-cpp to 2026-03-01#5.

This updates the registry port to consume the merged qvac-ext-stable-diffusion.cpp changes from:

tetherto/qvac-ext-stable-diffusion.cpp#6

What changed

• Updated stable-diffusion-cpp port REF to the merged sd.cpp commit.
• Bumped port-version from #4 to #5.
• Updated the versions database and baseline.

Motivation

Required for qvac diffusion addon PR:

tetherto/qvac#2245

The qvac PR needs the ESRGAN upscaler backend APIs from sd.cpp:

• sd_upscaler_device_t
• new_upscaler_ctx_with_device
• get_upscaler_backend_device

Validation

• git diff --check passed.
• JSON validation passed.
• vcpkg x-add-version passed.
• Local manifest install/download validation passed.
• vcpkg resolved stable-diffusion-cpp@2026-03-01#5.
• Source archive for the merged sd.cpp commit downloaded and extracted successfully.
• Extracted source contains the new ESRGAN upscaler APIs.

Full compile was not run locally because the ggml / stable-diffusion build is heavy.