fix: restore sustained search and public reader reliability

[unlockdigital]

Problem and behavior

Synchronous search handlers can accumulate wrappers under the previous FastAPI/Sentry combination and fail after sustained requests. This updates FastAPI to 0.142.1 and Sentry to 2.63.0, pins the required OpenTelemetry API dependency, and adds a real-integration regression covering 2,100 sequential requests, concurrent calls, and privacy-filtered exception capture.

Reader errors now render separately from empty results, with concise first-use guidance. Public web builds generate a minimal sitemap and matching robots directive using the configured site origin (local demo by default). Runtime health includes the API root filesystem with percentage and absolute-free thresholds, and a lightweight reader probe checks collection/search/sitemap behavior. Scheduling and alert delivery remain deployment responsibilities.

Validation

• Production-equivalent previous dependency stack reproduces failure around request 992; the corrected stack passes the sustained/concurrent regression and preserves event privacy filtering.
• Web: 138 unit tests, production build, and focused public-browse browser regression passed.
• Hosted-compatible source transplant: 124 unit tests and production build passed separately; no hosted collection content is included here.
• Seven local HTTP-server tests exercise the synthetic checker, including failure statuses, malformed responses, redirects and sitemap origin restrictions.
• Public fixture guard and diff checks pass. All four required CI gates passed at 43b0d8c (run38062247449): API PostgreSQL/Redis/migrations, web dependency/unit/build, browser regression, and clean demo with real API browser journey. Full and production npm audits report zero vulnerabilities.

Operational notes

No database migration or model/texture changes. Runtime-root health defaults to 85% used or 5 GiB free; container storage mapping determines whether it reflects host root capacity. Set VITE_PUBLIC_SITE_URL for a public deployment. The generic sitemap covers the homepage and object browser; publication-aware catalog exports remain a deployment step. Updated dependency notices are included. Owner review and normal protected merge are required.