fix: pin torch cu126 for GPU compatibility and fix cross-platform bugs

- Pin torch==2.6.0+cu126 and torchvision==0.21.0+cu126 in feature
  manifest to prevent NCCL symbol mismatch on CUDA 12.6 base images
- Move lpips after torch in install order to prevent wrong version
  resolution from PyPI
- Add einops to upscale-enhance common deps (required by SCUNet)
- Update cpu_fallback_packages to handle multi-package CUDA torch
  entries on amd64 without GPU
- Fix gpu.py ONNX CUDA detection: replace hardcoded .so path with
  cross-platform session smoke-test
- Fix os.dup(1) crashes on Windows in upscale, enhance_faces, and
  noise_removal by wrapping in try/except with sys.stderr fallback
- Guard top-level numpy/cv2 imports in colorize.py and restore.py
  with helpful error messages
- Add weights_only=False fallback for torch.load in noise_removal
- Fix integration tests to accept 501 for uninstalled AI features
  and 422 for missing system tools (exiftool, libheif)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/ai/python/restore.py

@@ -10,9 +10,14 @@ Multi-step pipeline for restoring old and damaged photos:
 import sys
 import json
 import os
-import numpy as np
-import cv2
-from PIL import Image
+
+try:
+    import numpy as np
+    import cv2
+    from PIL import Image
+except ImportError as _e:
+    print(json.dumps({"error": f"Missing dependency: {_e}. Install opencv-python-headless, numpy, and Pillow."}))
+    sys.exit(1)
 
 
 def emit_progress(percent, stage):