Run devdocs container as a subpath

# Feature request
Is it possible to run the DevDocs Docker container as a subpath? For example: https://example.com/devdocs

## Summary
Add environmental variable PATH_PREFIX(SCRIPT-NAME) or add special header for the reverse proxy (X-SCRIPT-NAME).

## Examples
https://example.com/devdocs

Start by tracing how the Docker container handles request paths and how deployment configuration reaches the application. Compare the requested PATH_PREFIX, SCRIPT-NAME, and X-SCRIPT-NAME approaches, then verify that the application works when served beneath /devdocs without breaking root-path behavior.

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