web: fix MeshCore ghost nodes (stale contact enrichment discarded)

[l5yth]

A node first heard via a bare MeshCore ADVERTISEMENT is upserted as a placeholder stamped lastHeard = now (receiver wall clock). The follow-up roster contact record carries lastHeard = last_advert — the sender-stamped advert-creation time, always older (seconds for healthy clocks, years for broken ones) — so upsert_node's row-level freshness guard discarded the entire named update, permanently: every contact re-post (auto-update re-fetch, periodic snapshot, restart) is also sender-stamped, while each advertised-position ingest re-bumps the row's last_heard. Result: nameless "ghost" nodes with hex short names, NULL role (displayed as the CLIENT default), and advert-stamped position_time — 22 of 48 meshcore nodes on dweb at the time of diagnosis.

Fix (web-side, protocol-neutral): after the guarded upsert, a non-synthetic record additionally fills identity columns that are still NULL (num, short_name, long_name, macaddr, hw_model, role, public_key, is_unmessagable). Stale records can fill gaps but never overwrite fresher values; synthetic chat placeholders remain barred from real rows; an empty MeshCore adv_name never fills long_name (NULLIF).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

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