Allow changing UV_HTTP_TIMEOUT

[TheCarpetMerchant]

Proposal

Downloading torch (2.0GiB)
× Failed to download torch==2.1.2+cu121
├─▶ Failed to extract archive: torch-2.1.2+cu121-cp310-cp310-linux_x86_64.whl
├─▶ I/O operation failed during extraction
╰─▶ Failed to download distribution due to network timeout. Try increasing
UV_HTTP_TIMEOUT (current value: 30s).

[NeuralFault]

Can set it as an environment variable that gets passed to every package at launch in Stability Matrix Settings > Package Environment section > Environment Variables and click Edit button. Then click the + button to add a row and put the variable name on the left half, and the value on the right half of the row.

When this gets brought up every once in a while, I tell users that need it to set it to 300 for the value.