chore(container): build in-tree ffmpeg CLI and route imageio through it (#10091)

[saturley-hall]

Cherry-pick of #10091 onto release/1.2.0.

Closes OPS-6862

What

Builds the ffmpeg CLI in-tree (LGPL-only: h264_nvenc + libvpx_vp9) and routes imageio through it via IMAGEIO_FFMPEG_EXE, replacing the GPL-encumbered prebuilt binary shipped by the imageio-ffmpeg wheel.

Cherry-pick notes

The release/1.2.0 base had refactored the container build since #10091 was authored, so five files conflicted. The resolution applies #10091's intent onto the new structure rather than its original line layout:

• requirements.trtllm.txt — kept deleted; trtllm now installs requirements.common.txt, which already carries the --no-binary imageio-ffmpeg directive.
• requirements.vllm.txt — kept the branch's vLLM multimodal deps; imageio handling lives in requirements.common.txt (installed in the same step).
• vllm_runtime.Dockerfile — added --reinstall-package imageio-ffmpeg to the existing requirements install, forcing a source rebuild that clears the base vllm image's GPL binary.
• trtllm_runtime.Dockerfile — added the ungated runtime ffmpeg-CLI copy + ENV IMAGEIO_FFMPEG_EXE, since the TRT-LLM diffusion handler unconditionally encodes video.
• wheel_builder.Dockerfile — added the nv-codec-headers + libvpx source build and switched ffmpeg ./configure to build the CLI with h264_nvenc/libvpx_vp9; the new NV_CODEC_HEADERS_REF/LIBVPX_REF args and the AWS_SDK_CPP_VERSION default now flow from args.Dockerfile/context.yaml.

Verified both the trtllm and vllm templates render cleanly via container/render.py.

🤖 Generated with Claude Code

---

[github-actions]

🌿 Fern Docs Preview: https://nvidia-preview-117fef14-fd3b-4b0b-8126-6a026a236543.docs.buildwithfern.com/dynamo/dev