refactor(files): improve efficiency/maintainability of ownership transfer share collection logic

[joshtrichards]

• Resolves: #

Summary

• Slightly improved performance (fewer DB calls, less intermediary memory).
• Slightly increased robustness (skips/fails on error per share, more consistent return).
• Improved code clarity/maintainability (unifies collector implementations, shares filter helper function, docs, streamline logic)
• UX: Better CLI progress and error visibility.

TODO

• ...

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)