Faster telemetry writes and statistics, one upstream send path, shared nginx config

[joszz]

Pull Request

Summary

The second batch (P2) from the project review; the first was #519.

• perf(telemetry): merging an MQTT message into its poll's row no longer reads the row (about eighty columns) first: the patch goes onto a key-only stand-in, so EF sends one UPDATE of just the fields the message carried. Checked against a real PostgreSQL: one UPDATE plus the pg_notify per message, where there was a SELECT too; a row that has gone still takes the patch as a new row. Buffering a whole poll in memory was considered and left out: the Worker's own checks read the row right after the write, and a crash would lose up to the merge window.
• perf(statistics): finished days' statistics are kept in memory per vehicle and time zone, and only the span the cache lacks is read; a statistics page opened again reads today rather than the whole period (up to ten years). A finished day cannot change, since every row is stamped when it arrives; a day counts as finished an hour after its local midnight, past the merge window. Documented under Caching in ARCHITECTURE.md.
• refactor(upstream): UpstreamRateGate.SendAsync waits out the interval, sends, and reads the answer for a slow-down; the five outside-service clients no longer repeat those steps by hand, and each keeps its own answer to being refused.
• perf(nginx): the frontend and all-in-one configs share one server body (frontend/nginx-app.conf) and only set their own $api_upstream. The build writes a .gz beside every compressible file at the highest level (scripts/precompress.mjs) and gzip_static serves it, instead of nginx compressing each response at level 1.
• refactor(data): the repositories demo mode shares with a real deployment are registered once.

Measured and left out: precompiling the vue-i18n messages saved under 1 KB gzipped on the entry bundle, not worth the new build dependency.

Type of Change

• Bug fix
• New feature
• Refactor / cleanup
• Documentation
• Dependency update
• Other (performance)

Related Issues

Follows #519.

Checklist

• Tests added or updated (SendAsync, fresh-context merges, the daily statistics cache)
• Linting passes (pnpm lint / dotnet build), plus dotnet format --verify-no-changes, 1432 backend and 1130 frontend tests
• No secrets or personal data committed
• Responsive on mobile (no layout changes)
• i18n keys added for any new UI strings (none added)
• If unraid/garagestack.xml changed: not changed

Also checked locally: both nginx configs pass nginx -t, and the frontend config, serving the real build, sends the prebuilt .gz byte for byte with Vary, the security headers and the cache headers. The Docker images and the Playwright smoke tests were not built or run locally (no Docker); CI covers them.

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