Version string is hardcoded in multiple places

[jtdub]

Problem

The version "0.1.0" is hardcoded as a string literal in two places in main.py:

• Line 11: version="0.1.0" (FastAPI app)
• Line 39: "version": "0.1.0" (root endpoint response)

These will drift from the canonical version in pyproject.toml.

Suggested Fix

Use importlib.metadata.version("hier-config-api") to read the version from the installed package metadata, or use a single __version__ constant in __init__.py.