refactor: store workspaces as {workspace_id}/{repo_name} for natural git clone layout

Working copies were stored as /data/working-copies/{repo_id}/{workspace_name}/,
so git clone was forced into a user-named directory. That meant the container
mount basename was the workspace name (e.g. main) instead of the repo name.

- Generate the workspace UUID before cloning and clone into
  /data/working-copies/{workspace_id}/ so git creates {repo_name}/ naturally
- Set workspace.path to /data/working-copies/{workspace_id}/{repo_name}/
- Update _migrate_clone_into_workspace() to use the same layout
- _get_repository_mount_name() now prefers workspace.path basename and only
  falls back to remote URL / repo.name for legacy repo-only instances
- Update unit tests to assert workspace path basename is used for mounts

Quality gates:
- pytest tests/unit: 219 passed
- ruff: clean on changed files
- mypy: clean on changed files

apps/api/src/services/.pi-map.md

@@ -4,11 +4,11 @@ dir: apps/api/src/services
 index: apps/api/src/services/.pi-map.index.md
 
 ## role
-This directory serves as the services layer for the API application, intended to contain business logic and service implementations.
+Service layer package for business logic implementation in the API application
 ## files
 - __init__.py | Empty file with no functionality
 ## arch
-The package follows a standard Python package structure with an empty `__init__.py` marker file, indicating it is a namespace package ready to house service modules, but currently contains no implemented services.
+Standard Python package structure with placeholder for service-oriented architecture; currently uninitialized with no implemented services
 ## tags
 init, empty, functionality
 ## symbols