Align env var names with DDE module standard

[laurencegoolsby]

Context

The DocumentAI API uses DOCUMENTAI_* prefixed env vars (DOCUMENTAI_INPUT_LOCATION, DOCUMENTAI_OUTPUT_LOCATION) while the template-infra DDE module provides standard DDE_* env vars (DDE_INPUT_LOCATION, DDE_OUTPUT_LOCATION, DDE_PROJECT_ARN, DDE_PROFILE_ARN). This mismatch requires a mapping layer in the infra config to alias one to the other.

Relates to navapbc/platform-test#278

Implementation

• Replace DOCUMENTAI_INPUT_LOCATION with DDE_INPUT_LOCATION
• Replace DOCUMENTAI_OUTPUT_LOCATION with DDE_OUTPUT_LOCATION
• Replace BDA_PROJECT_ARN with DDE_PROJECT_ARN
• Replace BDA_PROFILE_ARN with DDE_PROFILE_ARN
• Update all references in app code, env config, and tests