[Feature]: Add feature flag to disable chatbot routes and jobs in production

[mhd-hi]

Feature description

The chatbot is not ready yet and should not be exposed in production.

Proposed solution

Read a CHATBOT_ENABLED environment variable at startup. If false, all chatbot routes return 404. The variable is true in dev and staging, false in production.

A simple fix would be to add that feature toggle in chatbot-related modules and another one in the sync jobs sequence.

Definition of Done

• CHATBOT_ENABLED environment variable is read at startup
• Chatbot routes return 404 when CHATBOT_ENABLED=false
• Variable is correctly set in environment files (dev=true, staging=true, prod=false)