feat(API): Add root path support for web interface

[bbeiler-ridgeline]

This pull request adds support for specifying a custom root path for the DocStrange web interface, improving flexibility for deployments under subpaths (such as behind a reverse proxy). The changes include new CLI options, updates to user instructions and output, and configuration in the web server to honor the root path.

CLI enhancements

• Added a --root-path argument to the CLI, allowing users to specify a custom root path for the web interface (e.g., /docstrange). This is only used with the web command.

Web server configuration

• Updated the run_web_app function in docstrange/web_app.py to accept a root_path argument and configure the Flask application’s APPLICATION_ROOT accordingly. This ensures proper routing when the app is served under a subpath.
• Pass the root_path value to the static content (index.html, script.js) so that the frontend can hit the proper endpoints

Static Content

• Updated the index.html (template) to store the root_path for use on frontend resources
• Updated script.js to use the root_path if present (fallback to '') to make calls to the proper api location

@Siddhant011 @prats226