[refactor] Remove type pollution from ports with explicit boundary DTOs

[kangeunchan]

Enhancement Description

Replace interface{}-based port APIs with explicit boundary DTOs to restore type safety and correct dependency direction.

Background

Ports currently use interface{} in signatures and import plugin types, undermining compile-time safety and violating dependency inversion.

Scope

Replace interface{} in ports with explicit DTOs

• Files: internal/application/ports/provisioner.go
• Files: internal/application/ports/repositories.go
• Files: internal/application/ports/services.go

Introduce boundary DTOs and adapters

• Files: internal/application/dto/** (new, if needed)
• Files: internal/infrastructure/** (adapters converting plugin/infrastructure types to DTOs)

Remove plugin imports from ports

• Files: internal/application/ports/provisioner.go

Non-Goals

• Changing semantics of port methods beyond type changes
• Broad renaming across public APIs (keep changes minimal and localized)
• Refactoring unrelated infrastructure code

Risks and Open Questions

• DTO design must be stable and not leak infrastructure/plugin concerns
• Adapter conversions must be well-tested to avoid subtle field mapping bugs
• Some interface{} usage may be entrenched; prioritize most harmful ones first if needed

Validation Plan

Unit and Integration Checks

• go test ./... for ports, adapters, and affected use cases
• Unit tests ensuring DTO mapping correctness
• Compile-time checks confirming ports are plugin-free

End-to-End Checks

• Smoke: provisioning and other port-using flows still function
• Ensure no runtime type assertions remain in application layer

Evidence Required in Issue Updates

• Before/after examples of port signatures
• Evidence that ports no longer import plugin packages (go list/grep snippet)

Acceptance Criteria

• Zero interface{} in port signatures (logging varargs excluded)
• Ports do not import plugin packages
• All conversions occur in adapters
• Compiler/IDE type support improved (no type assertions in app layer)

Deliverables

• PR introducing DTOs and updating ports
• PR updating infrastructure adapters and wiring

[kangeunchan]

pull request: #122