fix(ci): namespace digest artifacts to avoid name collisions

[gclm]

## Summary

This PR fixes a GitHub Actions artifact name collision in the release workflows.

Previously, multiple reusable workflows uploaded digest artifacts using the same naming pattern:

- `digests-${module}-${arch}`

That becomes a problem when different workflow families resolve to the same module name in a single workflow run. For example:

- frontend: `providers/devbox` -> `devbox`
- service: `devbox`

Both can end up trying to upload an artifact named `digests-devbox-amd64`, which causes `actions/upload-artifact@v4` to fail with:

> 409 Conflict: an artifact with this name already exists on the workflow run

## Root Cause

The frontend workflow uses `basename(inputs.module)`, while service workflows use the module name directly.  
As a result, frontend and service builds can produce identical digest artifact names even though they belong to different workflow families.

## Changes

Namespace digest artifact names by workflow family and update the corresponding download patterns:

- frontend
  - upload: `frontend-digests-${{ env.MODULE_NAME }}-${{ matrix.arch }}`
  - download: `frontend-digests-${{ env.MODULE_NAME }}-*`

- service
  - upload: `service-digests-${{ inputs.module }}-${{ matrix.arch }}`
  - download: `service-digests-${{ inputs.module }}-*`

- service-rs
  - upload: `service-rs-digests-${{ inputs.module }}-${{ matrix.arch }}`
  - download: `service-rs-digests-${{ inputs.module }}-*`

## Why This Fix

This keeps the change narrowly scoped to CI artifact naming and avoids touching any build, push, or manifest logic.

Benefits:

- prevents cross-workflow artifact collisions in the same run
- keeps upload and download behavior aligned
- minimizes regression risk

## Verification

- confirmed the failing case was caused by artifact creation conflict, not image build failure
- verified upload names and download patterns are updated in all 3 related workflows
- parsed the modified workflow YAML files successfully
- performed a repository-wide check for related `digests-*` usage in the affected workflow family

## Notes

This change only affects internal CI artifact names. It does not change image tags, image repositories, or release output.

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