feat(realesrgan): add video upsampler integration

[gtong-nv]

Add Real-ESRGAN Upsampler Integration

Summary

Adds a new flashdreams-realesrgan workspace integration for Real-ESRGAN image and video upsampling. The integration provides a reusable Python API, an OpenCV-based realesrgan-upsample CLI, a FlashDreams video postprocessor config, focused CPU tests, and a checkpoint-backed GPU smoke script.

This also adds a generic flashdreams.infra.postprocess video chunk/postprocessor interface so Real-ESRGAN can plug into the same postprocessing shape as the FlashVSR work.

Changes

• Add integrations/realesrgan with RRDBNet/SRVGG architecture definitions compatible with public Real-ESRGAN checkpoints.
• Add RealESRGANUpsampler for frame-local RGB tensor upsampling, OpenCV BGR/BGRA/gray image handling, optional tiling, fp16 CUDA inference, and optional torch.compile.
• Add realesrgan-upsample CLI for image/video files with --compile, --compile-mode, and steady FPS profiling via --profile-warmup-frames.
• Add RealESRGANPostProcessorConfig for FlashDreams RGB video chunks.
• Optimize output conversion by emitting contiguous OpenCV-ready BGR/BGRA/gray arrays directly from tensors.
• Add integrations/realesrgan/scripts/gpu_smoke.py for real checkpoint/CUDA validation.
• Add third-party notices for Real-ESRGAN, BasicSR, and the optional OpenCV dependency.
• Register the new integration in workspace lock/type-check paths.

Notes

• The source port intentionally avoids copying the internal proprietary-header RealESRGAN source verbatim. The implementation is Apache-2.0 and references public Real-ESRGAN/BasicSR architecture compatibility.
• Real-ESRGAN is frame-local and does not need temporal chunks or future frames. The video CLI reads, upscales, profiles, and writes frames sequentially.
• The new standalone CLI preserves full 2x output dimensions. FlashVSR may crop output dimensions to 128-multiples and may drop trailing partial chunks in its standalone runner.

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