refactor: standardize delete return types across all domains

[iamfj]

Summary

Standardize the return type of all delete* service functions to return { id: string; success: boolean } instead of Promise<boolean>.

Context

During code review of #15 (comments edit/reply/delete), it was noted that deleteComment returns { id: string; success: boolean } while deleteAttachment, deleteDocument, and deleteIssueRelation return Promise<boolean>. The command layer then constructs a synthetic success object (e.g. outputSuccess({ success: true, message: "Document moved to trash" })).

The { id, success } pattern is better for JSON consumers — it confirms which entity was deleted and is consistent with how mutation payloads return entityId.

Affected Functions

Service	Current Return	File
deleteAttachment	Promise<boolean>	src/services/attachment-service.ts
deleteDocument	Promise<boolean>	src/services/document-service.ts
deleteIssueRelation	Promise<boolean>	src/services/issue-relation-service.ts
deleteComment	Promise<{ id, success }>	src/services/comment-service.ts ✅

Proposed Change

1. Update deleteAttachment, deleteDocument, deleteIssueRelation to return { id: string; success: boolean } (matching deleteComment).
2. Update their callers in the command layer to pass the returned object to outputSuccess() directly.
3. Update corresponding tests.

Acceptance Criteria

• All delete* service functions return { id: string; success: boolean }
• Commands pass the service result to outputSuccess() directly
• Tests updated
• npm run check:ci && npx tsc --noEmit && npm test && npm run build all pass