feat: Complete sprint 2 tasks

- Upgrade Python to 3.11 and update dependencies.
- Refactor main.py to isolate business logic.
- Fix bugs in flow_engine.py and printer.py.
- Improve database connection handling.
- Standardize error handling.
- Verify secret management.

Dockerfile

@@ -1,5 +1,5 @@
 # Python base image
-FROM python:3.9-slim
+FROM python:3.11-slim
 
 # Set working directory
 WORKDIR /talia_bot