refactor(infra): use Key Vault reference for chat system prompt #12

Job	Run time
Setup Environment	2s
Run Unit Tests with Coverage / Run Unit Tests	49s
Run API Contract Tests / Run API Contract Tests	29s
Build and Push Container Image / Build Container Image	1m 38s
Retrieve Container Image	22s
Run Bicep Linter / Lint Bicep Template	24s
Validate Template / Validate Bicep Template	25s
Preview Changes / Preview Bicep Template Deployment	46s
Deploy Template to Dev / Deploy Bicep Template	57s
Run E2E Tests Against Dev / Run E2E Tests with Cosmos DB Emulator	1m 10s
	7m 2s

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