fix: use --extra-index-url for PyTorch CUDA wheels in Docker requirements

--find-links does not act as a package index, so pip resolved torch
to the CPU-only PyPI version and failed to find torch==2.6.0+cu126.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: federicopalma-pro

docker/requirements.txt

@@ -13,5 +13,5 @@ langchain-core>=0.1.0,<1.0.0
 
 # PyTorch with CUDA support (pinned for GPU compatibility)
 # Using --find-links avoids dependency confusion risk of --extra-index-url
---find-links https://download.pytorch.org/whl/cu126
+--extra-index-url https://download.pytorch.org/whl/cu126
 torch==2.6.0+cu126