Add .env-example file and update configuration for environment variables

- Created .env-example for environment variable setup
- Updated README to reflect changes in .env file creation
- Modified config.py to include new environment variables and DATABASE_URL property
- Enhanced database.py with connect and disconnect functions
- Updated main.py to manage database connection lifecycle
- Adjusted compose.yaml for consistent environment variable usage

README.md

@@ -35,14 +35,14 @@ project/
 
 ### Setup
 
-Create a .env file in the root directory:
+Create a .env file, by copying .env-example, in the root directory and adjustign the vaulues as needed:
 
 ```text
-postgres_user=exampleUser
-postgres_password=examplePasswd
-postgres_db=exampleDB
-db_port=5432
-api_port=8000
+POSTGRES_USER=exampleUser
+POSTGRES_PASSWORD=examplePasswd
+POSTGRES_DB=exampleDB
+API_PORT=8000
+DEBUG=true
 ```
 
 Start the stack:
@@ -71,4 +71,4 @@ Do not run in production.
 The database schema is managed via Create.sql — no ORM migrations
 
 The .env file is excluded from version control via .gitignore
-```
+```