PixelProof v1.5.0: Solo-founder due-diligence fixes — health endpoint and JSON-LD schema

An Opus solo-founder due-diligence pass found that `/api/*/health` returned a 404 on every pick, which meant no uptime monitor could actually watch this app. `lib/api/health-check.ts` shipped as the one shared implementation behind all three pick health routes plus the root, checking database, Stripe, and email reachability with per-check timeouts so one slow dependency can't hang the whole probe.

JSON-LD schema also shipped on EntryProof and TariffWatch this release, closing a P0 finding from the same due-diligence pass that both picks were shipping zero structured data.