FFmpeg 7.1 + cuframes input demuxer

Snapshot FFmpeg n7.1 (release tag) с применённым patch'ем для cuframes
input format. Используется как FFMPEG_REPO_OVERRIDE в NickM-27/FFmpeg-Builds
fork для статической сборки patched binary под Frigate (Debian 12 / glibc 2.36).

Apply changes:
  + libavformat/cuframesdec.c (новый — реализация демуксера)
  M libavformat/Makefile (CONFIG_CUFRAMES_DEMUXER target)
  M libavformat/allformats.c (extern declaration)
  M configure (--enable-libcuframes option + dep check)

Patch source: https://git.goldix.org/gx/cuframes (filter/ffmpeg-7.1-cuframes-demuxer.patch)

History сброшена (snapshot вместо fork) потому что upstream shallow clone
не позволял push в gitea. Полная история FFmpeg — на github.com/FFmpeg/FFmpeg n7.1.

README.md

@@ -0,0 +1,46 @@
+FFmpeg README
+=============
+
+FFmpeg is a collection of libraries and tools to process multimedia content
+such as audio, video, subtitles and related metadata.
+
+## Libraries
+
+* `libavcodec` provides implementation of a wider range of codecs.
+* `libavformat` implements streaming protocols, container formats and basic I/O access.
+* `libavutil` includes hashers, decompressors and miscellaneous utility functions.
+* `libavfilter` provides means to alter decoded audio and video through a directed graph of connected filters.
+* `libavdevice` provides an abstraction to access capture and playback devices.
+* `libswresample` implements audio mixing and resampling routines.
+* `libswscale` implements color conversion and scaling routines.
+
+## Tools
+
+* [ffmpeg](https://ffmpeg.org/ffmpeg.html) is a command line toolbox to
+  manipulate, convert and stream multimedia content.
+* [ffplay](https://ffmpeg.org/ffplay.html) is a minimalistic multimedia player.
+* [ffprobe](https://ffmpeg.org/ffprobe.html) is a simple analysis tool to inspect
+  multimedia content.
+* Additional small tools such as `aviocat`, `ismindex` and `qt-faststart`.
+
+## Documentation
+
+The offline documentation is available in the **doc/** directory.
+
+The online documentation is available in the main [website](https://ffmpeg.org)
+and in the [wiki](https://trac.ffmpeg.org).
+
+### Examples
+
+Coding examples are available in the **doc/examples** directory.
+
+## License
+
+FFmpeg codebase is mainly LGPL-licensed with optional components licensed under
+GPL. Please refer to the LICENSE file for detailed information.
+
+## Contributing
+
+Patches should be submitted to the ffmpeg-devel mailing list using
+`git format-patch` or `git send-email`. Github pull requests should be
+avoided because they are not part of our review process and will be ignored.