Get pipeline working

## Purpose This PR adds env variables that were missing from the azd pipeline, and updates AGENTS.md with tips for keeping env variables in sync. ## Does this introduce a breaking change? When developers merge from main and run the server, azd up, or azd deploy, will this produce an error? If you're not sure, try it out on an old environment. ``` [ ] Yes [X] No ``` ## Type of change ``` [X] Bugfix [ ] Feature [ ] Code style update (formatting, local variables) [ ] Refactoring (no functional changes, no api changes) [ ] Documentation content changes [ ] Other... Please describe: ``` ## Code quality checklist See [CONTRIBUTING.md](https://github.com/Azure-Samples/rag-postgres-openai-python/blob/main/CONTRIBUTING.md#submit-pr) for more details. N/A