fix(pwa): deterministic build id; data log newest-first; README scree…

[Fyfar]

…nshot

• next.config.ts: pin a content-derived generateBuildId. Next's default buildId is random per build and is baked into index.html + the _next/static// path, both precached — so the service worker's content-version changed on every build (even docs-only commits or CI re-runs), prompting every client to "Reload" with nothing actually to update. Hashing the build inputs makes the SW version stable across rebuilds of identical source while still changing on real app changes; unlike a constant id it keeps online users safe (new content → new asset folder).
• DataLog: render measurements newest-first (latest on top, oldest at the bottom); display-only — the underlying dataset, chart, stats, and CSV stay chronological.
• README: add interface screenshot near the top + expand the PWA install/offline section (no native .exe/.dmg needed).
• bump version 1.0.4 → 1.0.5 (single bump for the session); realign stale package-lock version.