chore(env): Present example env file properly

.env.example

@@ -0,0 +1,12 @@
+# .env (in the root directory)
+
+# MariaDB Credentials (used by docker-compose to init the DB)
+MARIADB_ROOT_PASSWORD=supersecretroot
+MARIADB_DATABASE=lms_db
+MARIADB_USER=lms_user
+MARIADB_PASSWORD=lms_password
+
+# Backend Configuration (can override defaults)
+# SERVER_ADDR=0.0.0.0:8080 # Already set in compose file
+RUST_LOG=info,lms_backend=debug # Example: Set backend log level to debug
+# SECRET_KEY=your_secret_for_jwt_if_used # Needed if switching to JWT sessions