feat(resumes): variants, labels, and clearer resume selection on applications

[leobrqz]

Summary

Treat uploaded resumes as versioned or labeled variants (e.g. “Backend v3”) and make application forms clearly select “which file was used” for that application. Optional later tie-in: suggested default per platform when manual_resume is relevant.

resume_id already links an application to a file; users still think in versions and roles. Naming and discovery reduce mistakes when multiple PDFs exist.

Proposed behavior

• Resume library supports a display label or version tag in addition to display name, without breaking uniqueness rules already enforced on names if that constraint stays.
• Application form resume picker shows distinguishable labels (and maybe upload date or short description).
• Optional: platform settings include a “default resume for new applications on this platform” that pre-selects but remains overridable.

Scope notes

• File storage and download paths stay internal; API responses continue to omit internal paths.
• First version can defer per-platform default if it simplifies delivery.

Success criteria

• User with multiple resumes can tell them apart in the picker and in the profile list.
• Selected resume on an application is obvious when revisiting the edit dialog.