Make check-url available in configuration files (#9032)

## Summary

Fixes #9027

Minor enhancement on top of #8531 that makes the CLI parameter
`--check-url` also available as the setting `check-url` in configuration
files.

## Test Plan

Updates existing tests to take the new setting into account.

Within publish command testing I didn't see existing tests covering
settings from toml files (instead of from CLI params), so I didn't add
anything of that sort.

docs/reference/settings.md

@@ -457,6 +457,42 @@ globs are interpreted as relative to the project directory.
 
 ---
 
+### [`check-url`](#check-url) {: #check-url }
+
+Check an index URL for existing files to skip duplicate uploads.
+
+This option allows retrying publishing that failed after only some, but not all files have
+been uploaded, and handles error due to parallel uploads of the same file.
+
+Before uploading, the index is checked. If the exact same file already exists in the index,
+the file will not be uploaded. If an error occurred during the upload, the index is checked
+again, to handle cases where the identical file was uploaded twice in parallel.
+
+The exact behavior will vary based on the index. When uploading to PyPI, uploading the same
+file succeeds even without `--check-url`, while most other indexes error.
+
+The index must provide one of the supported hashes (SHA-256, SHA-384, or SHA-512).
+
+**Default value**: `None`
+
+**Type**: `str`
+
+**Example usage**:
+
+=== "pyproject.toml"
+
+    ```toml
+    [tool.uv]
+    check-url = "https://test.pypi.org/simple"
+    ```
+=== "uv.toml"
+
+    ```toml
+    check-url = "https://test.pypi.org/simple"
+    ```
+
+---
+
 ### [`compile-bytecode`](#compile-bytecode) {: #compile-bytecode }
 
 Compile Python files to bytecode after installation.