feat(status): 24-hour activity sparklines on worker pulse cards

Each worker card on /status now renders a stacked-bar histogram of the
last 24 hourly buckets — successes from the bottom up in primary blue,
failures from the top down in destructive red, idle hours as a thin
baseline.  Heights normalise to the loudest hour in the series so quiet
workers still show shape.

- /api/status/workers: extended the response with activity24h per
  worker, computed via a generate_series CTE joined to analyzer_jobs /
  rmm_executions / sync_history (zero-fill so the 24-bucket shape is
  consistent regardless of activity).
- ActivitySparkline (components/status/activity-sparkline.tsx) — pure
  flex-end bar strip, no recharts dependency, 32px tall by default.
- WorkerPulse renders the strip below the in-flight / 1h tiles with
  "24h ago" / "now" labels.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

DESIGN.md

@@ -363,6 +363,10 @@ below is the working backlog; expand as we go.
       logged, ticket touch count).
 - [x] ~~Worker pulse section on `/status`~~ — analyzer / RMM / sync
       scheduler heartbeats via `/api/status/workers` and `WorkerPulse`.
+- [x] ~~Worker activity sparklines~~ — `ActivitySparkline` shows 24
+      hourly buckets per worker (success bottom-up in primary, failure
+      top-down in destructive). Backed by zero-filled hour series
+      generated in the `/api/status/workers` query.
 
 ### Tokens & theming
 - [-] Hard-coded Tailwind palette colors are extensive (~770 references)