Support Docker build context from non-root directory

[myakove]

Summary

Add support for building Docker images when the Dockerfile and build context are in a subdirectory (e.g., docker/) rather than the repository root.

Problem

Currently, the webhook server assumes the Dockerfile is at the repo root. If a project places its Dockerfile in a subdirectory like docker/, the build fails or requires workarounds (keeping the Dockerfile in root).

Expected Behavior

Allow configuring the Docker build context path per repository, e.g.:

• docker build -t image docker/ (context = docker/)
• docker build -f docker/Dockerfile -t image . (Dockerfile path + root context)

Use Case

myk-org/pi-config has a Dockerfile + entrypoint.sh that logically belong in a docker/ subdirectory but are currently kept at root due to this limitation.