feat: Implement core application structure, AI extraction, persistence, and Telegram bot modules with updated configuration and dependencies.

app/config.py

@@ -0,0 +1,36 @@
+"""
+Configuration loader.
+
+Loads environment variables from a .env file and makes them available as a Config object.
+"""
+import os
+from dotenv import load_dotenv
+
+# Load environment variables from .env file in the project root
+# Note: The path is relative to the file's location in the final `app` directory
+dotenv_path = os.path.join(os.path.dirname(os.path.dirname(os.path.abspath(__file__))), '.env')
+if os.path.exists(dotenv_path):
+    load_dotenv(dotenv_path)
+
+class Config:
+    """
+    Holds the application's configuration.
+    """
+    # Telegram Bot Token
+    TELEGRAM_TOKEN = os.getenv("TELEGRAM_TOKEN")
+    
+    # OpenAI API Key
+    OPENAI_API_KEY = os.getenv("OPENAI_API_KEY")
+
+    # Supergroup ID for the bot
+    SUPERGROUP_ID = os.getenv("SUPERGROUP_ID")
+    
+    # Database URL (e.g., "sqlite:///expenses.db")
+    DATABASE_URL = os.getenv("DATABASE_URL", "sqlite:///../database.db")
+
+    # Log level
+    LOG_LEVEL = os.getenv("LOG_LEVEL", "INFO")
+
+
+# Create a single instance of the configuration
+config = Config()