Complete GitLab discussion/finding coverage #1881

Feature / improvement for Solenta. Priority: Medium. Area: Review and GitLab.

Include file-level, image and unresolved overview discussions; mark discussions outdated when their position no longer matches the MR diff refs. Keep them actionable as findings.

Acceptance criteria:

• Implement the described behavior through the existing shared APIs and UI, preserving current explicit settings and account/permission boundaries.
• Cover the changed behavior with focused regression checks, including the stated edge cases and compatibility paths.
• Run the relevant checks and typecheck for code changes; verify visible UI behavior when affected.

Part of #1869.