fix(settings): load .env from repo root instead of project dir

mnemosyne/mnemosyne/settings.py

@@ -23,8 +23,9 @@ env = environ.Env(
     DEBUG=(bool, True),
 )
 
-# Read .env file if it exists
-environ.Env.read_env(BASE_DIR / ".env")
+# Read .env file if it exists. Lives at the repo root (one level above the
+# Django project package), shared with the docker-compose stack.
+environ.Env.read_env(BASE_DIR.parent / ".env")
 
 # --- Security ---
 SECRET_KEY = env("SECRET_KEY", default="django-insecure-change-me-in-production")