VPR-74 chore(deps): upgrade AWS SDK from v3 to v4

[rlorenzo]

Summary

Upgrades the AWS SDK for .NET from v3 to v4 in both projects that reference it (Viper and EffortMigration):

• AWSSDK.Core 3.7.201.7 -> 4.0.100
• Amazon.Extensions.Configuration.SystemsManager 5.1.0 -> 7.1.0 (the SDK-v4 line)

Core is pinned to 4.0.100 rather than the latest 4.0.100.2, which was published under the 7-day supply-chain bake window at review time; the delta is routine service-model updates and can be picked up in a later bump.

No code changes were needed: our AWS surface (SSM Parameter Store config load, AwsSsmHealthCheck, credential profile registration) uses no APIs removed in v4.

Breaking changes reviewed

• SDK v4 migration guide: nullable value types, collections defaulting to null, STS/S3/DynamoDB changes - none apply to our usage.
• SystemsManager extension crosses two majors: 6.0.0 splits StringList parameters into indexed keys; 6.2.0 throws at startup on case-insensitive duplicate parameter keys under a loaded path. Neither affects the current /Development + /Shared parameter sets.

Verification

• npm run verify:build: 0 errors; npm run test:backend: 2140/2140 passed
• Booted the app locally: clean startup with config loaded from SSM, /health/detail fully Healthy including aws-ssm (live v4 GetParametersByPath call) and all nine db-* checks (DB passwords delivered via SSM)
• Confirmed the running process loaded AWSSDK.Core 4.0.100.0, SystemsManager 7.1.0.0, and transitive AWSSDK.SimpleSystemsManagement 4.0.6.11

JIRA: https://ucdsvm.atlassian.net/browse/VPR-74

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 45.29%. Comparing base (8991c34) to head (5096a64).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #256   +/-   ##
=======================================
  Coverage   45.29%   45.29%           
=======================================
  Files         897      897           
  Lines       51929    51929           
  Branches     4879     4879           
=======================================
  Hits        23522    23522           
  Misses      27803    27803           
  Partials      604      604           

Flag	Coverage Δ
backend	45.39% <ø> (ø)
frontend	43.41% <ø> (ø)

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[codecov-commenter]

Bundle Report

Bundle size has no change ✅

[rlorenzo]

@bsedwards I thought this would involve a breaking API change since this is a major version, but updating the package works out of the box with no changes needed. Working on the TEST server as well.