feat(robots): manage cloud asset binding

[shark0F0497]

Summary

• add backend APIs for listing, binding, changing, and unbinding robot cloud asset IDs
• validate bindable device IDs from the DP config and enforce active robot uniqueness
• resolve sync uploads from the current robot asset binding before falling back to legacy episode metadata
• update the cloud sync design document

Verification

• GOCACHE=/tmp/go-build-cache go test ./internal/services ./internal/api/handlers ./internal/server -run 'Test(ResolveAssetIDForEpisode|EnqueueEpisode|MarkSync|RobotHandler|ListDPDeviceProfiles|LoadDPDeviceUploadConfig|ParseDPResolvedEndpoint)' -v\n- git diff --check\n\n## Notes\n- Swagger docs were not regenerated because the local swag CLI is not installed.