fix: Dashboard-api module-level aiohttp/httpx clients never closed on shutdown

[patil2001]

Summary

Module-level clients created at import; no close on app shutdown.

Impact: Production user/operator failure on Osmantic/ODS main

Files:

• dashboard-api/helpers.py (:88-122)
• main.py lifespan

Repro

On a production-like Osmantic/ODS main checkout:

1. Hit the failure mode described in Summary (severity: Medium).
2. Observe the broken behavior / incorrect exit / missing guard from the root cause above.
3. Confirm no overlapping open PR (dedup: No open issue. No open PR.).

Fix

Implement a minimal, distro-/path-correct fix in the listed files (no scope creep).

• Address the root cause directly (do not paper over with || true / broad catches).
• Prefer resolving runtime values from the environment/repo (like apt-cache madison) over hardcoding distro-specific version strings when the same bug class applies.
• Add a regression test under ods/tests/ (or matching suite) that fails without the fix and passes with it.

Context

Filed from Desktop issues.md entry #33 via one-click scout pipeline.
Rationale: Unfiled Desktop issues.md #33 (no GitHub issue yet)