[DERCBOT-1904] Add bot business rules configuration API

[scezen]

Ticket : DERCBOT-1904

Goal

Add backend storage, APIs, and RAG prompt injection for bot business rules used by GenAI/RAG configuration.

Details

• Add a new Mongo collection for business rules, indexed by namespace and botId
• Store covered topics, excluded topics, and lexicon groups per bot
• Add a GET endpoint: /gen-ai/bots/:botId/configuration/business-rules
• Add a POST endpoint for create/update on the same path
• Use POST as a full replacement of the business rules configuration
• Clean up the business rules configuration when deleting an application
• Load and cache business rules configuration like the other GenAI bot configs
• Refresh the cached business rules when the Mongo configuration changes
• Inject covered_topics and excluded_topics into the RAG question-answering prompt inputs