feat: document_url support local path

[MingruiZhang]

No description provided.

[Copilot]

Pull Request Overview

This PR adds support for local file paths in document_url and markdown_url parameters by automatically converting them to file parameters when they reference existing local files.

• Adds a utility function to detect and convert local file paths to file objects
• Integrates the conversion logic into both sync and async extract/parse methods
• Maintains backward compatibility by preserving remote URLs unchanged

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
src/landingai_ade/lib/url_utils.py	New utility module with URL-to-file conversion logic
src/landingai_ade/_client.py	Integration of URL conversion in client methods

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