Simplified AgentOS configuration: use a single db parameter

AgentOS now uses a unified db parameter and deprecates tracing_db. This reduces configuration complexity and clarifies data storage for both operational and tracing needs.

Details:

• Replace tracing_db with db in configuration
• Aligns all AgentOS data under a single, explicit database setting

Who this is for: Platform teams managing AgentOS deployments who want simpler, less error-prone configuration.