/admin/data draws the facts: overview strip, precision, latency, people and health charts, worst sessions, on phone, tablet and desktop #530

Third piece of #508: the page itself. Take src/data-page.ts and src/ui/data-view.js from branch quill/508-a-data-view-to-explore-the-arm-people-pr (74967da).

Done when:

• [ ] /admin/data is linked from /admin and from the Admin tab. Its SVG is drawn by hand, with no new dependency, and its inline style and script are pinned by hash under a default-src 'none' CSP.
• [ ] It has the Hour, Day, Week and All ranges, drag to zoom, compare to the period before, exact values on hover, tap or arrow keys, version marks on every time axis, and a worst-sessions table that opens the session's numbers and events.
• [ ] Layout: one column with swipeable cards on a portrait phone, two columns in landscape and on a tablet, three on a desktop. Both colour schemes, motion only under no-preference, and nothing covers the camera.
• [ ] data-layout.test.ts passes, bun scripts/design-lint.ts is clean where it applies, and bun --cwd Software/so101 test passes.

Brief: a builder with the page's design notes.