Fix .env file loading for CLI environment variables

- Add load_dotenv() call at module import to load .env before Click
  processes envvar parameters
- Add python-dotenv>=1.0.0 as explicit dependency in pyproject.toml

Click's envvar only reads from OS environment, not .env files.
By loading dotenv early, all CLI commands now respect .env configuration.

pyproject.toml

@@ -28,6 +28,7 @@ dependencies = [
     "click>=8.1.0",
     "pydantic>=2.0.0",
     "pydantic-settings>=2.0.0",
+    "python-dotenv>=1.0.0",
     "sqlalchemy>=2.0.0",
     "alembic>=1.12.0",
     "fastapi>=0.100.0",

src/meshcore_hub/__main__.py

@@ -1,11 +1,15 @@
 """MeshCore Hub CLI entry point."""
 
 import click
+from dotenv import load_dotenv
 
 from meshcore_hub import __version__
 from meshcore_hub.common.config import LogLevel
 from meshcore_hub.common.logging import configure_logging
 
+# Load .env file early so Click's envvar parameter picks up values
+load_dotenv()
+
 
 @click.group()
 @click.version_option(version=__version__, prog_name="meshcore-hub")