Handle malformed FHIR extension URLs and improve local troubleshooting

[yuliumitre]

This PR includes several fixes that should help other developers load and troubleshoot pseudoEHR data more reliably:

1. Sanitizes incoming FHIR JSON responses by removing extension / modifierExtension entries with blank URLs before fhir_models parses them.
2. Fixes ADI and $everything parsing failures caused by url: null extensions in external FHIR payloads.
3. Improves sample data push reliability by using explicit Net::HTTP timeouts and SSL certificate store handling.
4. Surfaces OperationOutcome diagnostics when QR-to-PFE conversion fails.
5. Adds scripts/start_pseudo_ehr.sh to simplify local startup, including PostgreSQL startup and DB preparation.