Smart GIF Optimizer minimal FFmpeg build

FFmpeg: 8.1.2
Build recipe: scripts/build-ffmpeg-minimal.ps1
Toolchain: w64devkit 2.7.0 (GCC 15.2.0), NASM 2.16.03
External libraries: libvpx 1.16.0, zlib 1.3.2
License reported by `ffmpeg -L`: GNU LGPL version 2.1 or later

The build disables everything first and enables only the program, demuxers,
decoders, encoders, filters, parsers, muxers, protocols and bitstream filters
required by Smart GIF Optimizer. It does not enable GPL, nonfree, version3,
libx264, libx265 or libfdk components.

The Windows linker uses `--no-insert-timestamp`. Because GNU strip rewrites
that field, the build script also normalizes the final PE timestamp and the
unused executable checksum to zero. Clean builds therefore produce a stable
binary SHA-256 without changing the program sections.

Run `npm run verify:licenses` before every distribution build. The verifier
checks the build configuration, required capabilities, versions and binary
SHA-256 values against ThirdParty/manifest.json.