refactor(usecase): migrate show operations to provider interfaces

[mpyw]

Summary

• Migrate show usecases to use provider interfaces
• Move version resolution logic to paramversion and secretversion packages
• Add shared shift resolution helper in version/internal

Changes

Version Package Updates

• version/internal/resolve.go: New ApplyShift helper for shared shift logic
• paramversion/resolve.go: New Resolve function using provider.ParameterReader
• secretversion/resolve.go: New Resolve function using provider.SecretReader

Show Migration

• usecase/param/show.go: Use paramversion.Resolve instead of local resolver
• usecase/secret/show.go: Use secretversion.Resolve instead of local resolver
• Remove usecase/param/version_resolver.go (moved to paramversion)
• Simplify usecase/secret/version_resolver.go (keep only VersionResolverClient for diff/log)

Unchanged (for future PRs)

• diff.go and log.go still use old AWS SDK types
• VersionResolverClient kept for backward compatibility

Test plan

• make test passes
• make lint passes

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 80.66298% with 35 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.39%. Comparing base (53ecc39) to head (ac8a207).

Files with missing lines	Patch %	Lines
internal/version/secretversion/resolve.go	61.22%	10 Missing and 9 partials ⚠️
internal/version/paramversion/resolve.go	77.27%	5 Missing and 5 partials ⚠️
internal/usecase/param/show.go	87.50%	1 Missing and 1 partial ⚠️
internal/usecase/secret/show.go	87.50%	1 Missing and 1 partial ⚠️
internal/version/internal/resolve.go	60.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@              Coverage Diff               @@
##           multicloud     #149      +/-   ##
==============================================
+ Coverage       87.14%   88.39%   +1.24%     
==============================================
  Files             139      144       +5     
  Lines            8170     8306     +136     
==============================================
+ Hits             7120     7342     +222     
+ Misses            806      696     -110     
- Partials          244      268      +24     

Flag	Coverage Δ
e2e	66.21% <78.45%> (+1.46%)	⬆️
platform-darwin	64.38% <ø> (ø)
platform-linux	62.85% <ø> (ø)
platform-windows	73.46% <ø> (ø)
unittests	76.22% <70.71%> (-0.21%)	⬇️

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[mpyw]

Closing this PR due to design issue: AWS-specific knowledge (ARN, Type) leaking into provider-agnostic Resource model.

Root cause: model.Secret.ARN and model.Parameter.Type are already AWS-specific in base models. Need to fix model design first (move to Metadata) before retrying show unification.

Tag migration (PR #147) is kept as it doesn't have this problem.