Overlay deploy/restart event annotations on Status charts

Studio already knows about deployments and instance restarts. Vertical reference lines on the time axis ("deployed v2.3", "node-3 restarted") turn correlation hunting ("did the error spike start at the deploy?") into reading. `LineChart` already renders `ReferenceLine`s for thresholds — this adds a time-keyed variant fed by the deployments/instance-events data, with a legend/toggle to declutter.

## Acceptance criteria
- Time-series charts can show vertical markers for deployment events within the window, with a toolbar toggle (default on); hovering a marker identifies the event and timestamp.
- At most one deployments query per Status page view (shared, not per panel).
- If instance-restart data is available cheaply (investigate `get_status`/system events), include restarts; otherwise ship deploys only and note the follow-up.

## Implementation notes
- Deployments API exists: `src/integrations/api/instance/deployments/listDeployments.ts`.
- `LineChart` already renders `ReferenceLine`s for thresholds — add a time-keyed variant (x= instead of y=) threaded via `AnalyticsContext` → `MetricRenderer`.

Filed from a Status tab code review.

Comment generated by kAIle (Claude Fable 5)