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/upscale.py

@@ -94,8 +94,14 @@ def main():
                 # Libraries like basicsr, realesrgan, gfpgan, and torch print
                 # download progress and init messages to stdout which would
                 # corrupt our JSON result.
-                stdout_fd = os.dup(1)
-                os.dup2(2, 1)
+                stdout_fd = None
+                try:
+                    stdout_fd = os.dup(1)
+                    os.dup2(2, 1)
+                except OSError:
+                    # os.dup may fail on Windows with piped stdio
+                    stdout_fd = None
+                sys.stdout = sys.stderr
 
                 try:
                     from basicsr.archs.rrdbnet_arch import RRDBNet
@@ -166,8 +172,10 @@ def main():
 
                 finally:
                     # Restore stdout after ALL AI processing
-                    os.dup2(stdout_fd, 1)
-                    os.close(stdout_fd)
+                    if stdout_fd is not None:
+                        os.dup2(stdout_fd, 1)
+                        os.close(stdout_fd)
+                    sys.stdout = sys.__stdout__
 
             except (ImportError, FileNotFoundError, RuntimeError, OSError) as e:
                 import traceback