Refactor augmentation Lambda to read from S3 instead of SQS body

[nickclyde]

Summary

Closes #418

• Rewrites the augmentation Lambda to be triggered by S3 events (via EventBridge → SQS) instead of receiving inline eICR XML and nonstandard codes in the SQS message body
• Lambda now reads TTC output from TTCAugmentationMetadataV2/{persistenceId} and the original eICR from eCRMessageV2/{persistenceId}, matching the APHL AIMS eCR pipeline architecture
• Implements source-bucket routing (extracts bucket name from S3 event, falls back to S3_BUCKET env var)
• Adds Terraform resources for the full event pipeline: SQS queue + DLQ, EventBridge rule on TTCAugmentationMetadataV2/ prefix, Lambda event source mapping, IAM policy, and S3 EventBridge notification
• Fixes existing Terraform bug where REGION env var was used instead of AWS_REGION (which lambda_handler.create_s3_client() expects)

Changes

packages/augmentation-lambda/

• lambda_function.py: Complete rewrite — parses EventBridge S3 events from SQS, reads inputs from S3 via lambda_handler helpers, adds _parse_nonstandard_codes() to validate TTC output entries as NonstandardCodeInstance objects
• pyproject.toml: Added aws-lambda-powertools, structlog deps; added boto3, moto dev deps
• tests/conftest.py (new): moto mock_aws fixtures with EventBridge S3 event payloads and pre-populated S3 test data
• tests/test_augmentation_lambda_function.py: Rewritten with 10 tests covering success, S3 writes, source-bucket routing, missing files, mixed batch, and _parse_nonstandard_codes parsing

terraform/

• main.tf: Added EICR_INPUT_PREFIX and TTC_OUTPUT_PREFIX env vars, fixed REGION → AWS_REGION, added SQS queue + DLQ, EventBridge rule, event source mapping, and SQS IAM policy
• s3.tf: Enabled EventBridge notifications on the S3 bucket

[codecov-commenter]

Codecov Report

❌ Patch coverage is 96.49123% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.75%. Comparing base (d031555) to head (ad36342).

Files with missing lines	Patch %	Lines
...-lambda/src/augmentation_lambda/lambda_function.py	96.49%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #424      +/-   ##
==========================================
- Coverage   95.78%   95.75%   -0.03%     
==========================================
  Files          42       42              
  Lines        2183     2216      +33     
==========================================
+ Hits         2091     2122      +31     
- Misses         92       94       +2     

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