Fix TFLint violations: terraform_required_providers warnings across edge modules

[WilliamBerryiii]

Summary

After replacing MegaLinter with per-tool GitHub Actions lint workflows (#235, PR #240), the Terraform Lint job revealed pre-existing terraform_required_providers TFLint warnings in edge infrastructure modules. These violations are currently soft-failed in PR validation.

Details

The terraform-lint.yml reusable workflow runs tflint --recursive with the terraform ruleset. The following pattern was flagged:

• Rule: terraform_required_providers — Missing version constraint for provider azurerm in required_providers
• Location: src/100-edge/120-observability/terraform/modules/rule-associations-obs/main.tf (and potentially other internal modules)

Acceptance Criteria

• All TFLint terraform_required_providers warnings are resolved
• npm run tflint-fix-all passes cleanly
• Terraform Lint job in PR validation passes without soft-fail: true
• Remove soft-fail: true from terraform-lint in .github/workflows/pr-validation.yml

References

• PR build(ci): replace MegaLinter with per-tool GitHub Actions lint workflows #240 — MegaLinter replacement
• Issue ci(lint): replace MegaLinter with dedicated per-tool GitHub Actions workflows #235 — Parent issue
• TFLint rule docs