fix: auto-load .env file for PyPI installations

PyPI users running `mcphub` had to manually export env vars because
server.py didn't call load_dotenv(). Docker users were unaffected
since docker-compose loads .env automatically.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "mcphub-server"
-version = "3.0.2"
+version = "3.0.3"
 description = "AI-native management hub for WordPress, WooCommerce, and self-hosted services via Model Context Protocol (MCP)"
 authors = [
     {name = "MCP Hub", email = "contact@mcphub.dev"}