Single-user mode: pod should be served at server root, not /me/ #348

Summary

In --single-user mode, JSS currently mounts the pod at /me/ rather than at the server root /. Since single-user mode means exactly one pod, the /me/ path prefix has no namespace-disambiguation purpose and adds friction for clients that expect a pod root to coincide with the server origin.

Current Behavior

$ jss start --single-user
# Pod resources accessible at:
#   http://localhost:4000/me/
#   http://localhost:4000/me/profile/card
#   http://localhost:4000/me/.acl

Expected Behavior

$ jss start --single-user
# Pod resources accessible at the server origin:
#   http://localhost:4000/
#   http://localhost:4000/profile/card
#   http://localhost:4000/.acl

The single-user pod's storage root coincides with the server origin — which is the natural mapping when there is, by definition, exactly one user.

Rationale

• No namespace conflict: single-user means one pod; /me/ adds nothing
• Cleaner WebID URIs: https://my.example.org/profile/card#me rather than https://my.example.org/me/profile/card#me
• Standard Solid pod-at-origin pattern: matches what most existing Solid clients and tutorials assume
• Clean offline-export and static-site behavior: a saved page's URI matches the server origin

Acceptance

• --single-user (without other path-related overrides) serves the pod at /
• WebID at /profile/card#me
• Root ACL at /.acl
• Container listing of / returns the LDP container for the pod root
• Multi-user mode unchanged