Add config and client injection with test reorganization.

Introduce typed config objects, optional adapter injection, and .env loading to simplify testing while preserving env-based defaults for production usage.

Co-authored-by: Cursor <[email protected]>

python_repositories/config/dotenv_loader.py

@@ -0,0 +1,14 @@
+"""Load environment variables from a .env file."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+from dotenv import load_dotenv as _load_dotenv
+
+
+def load_dotenv(path: str | Path | None = None) -> bool:
+    """Load .env into os.environ. Idempotent; returns True if a file was loaded."""
+    if path is None:
+        return bool(_load_dotenv())
+    return bool(_load_dotenv(path))