Admin UI: per-attempt timeline view with trace link-out

[hardbyte]

Motivation

The queue-storage engine already records a rich evidence trail per attempt — receipts, lease claims, closures, heartbeats, callback park/resume, terminal evidence — but the UI presents jobs as state snapshots. Turning the evidence trail into a timeline is the operator-UX payoff of the storage design, and pairs directly with end-to-end tracing (#110): the timeline is where a trace id becomes clickable.

Scope

• Per-job "Attempts" view assembling, per attempt: claim (receipt or lease), heartbeats, progress updates, snoozes, callback park/resume, deadline/rescue events, finalization (with run_lease identity), retry scheduling.
• Sourced from the public read surfaces (terminal_jobs, lease/receipt views) — no direct dependence on internal physical layout (per ADR-026's public-surface rule).
• Trace link-out: when Tracing #110's trace_context is present, render a configurable link template (AWA_TRACE_URL_TEMPLATE, e.g. Grafana Tempo/Jaeger URL with {trace_id}).
• API endpoints land in the awa-api crate (Split awa-api from awa-ui: separate API response types from embedded frontend #143) as versioned response types.

Acceptance

• A retried job with a callback park shows a complete, ordered timeline across both attempts.
• Timeline renders correctly for receipt-path (short) and lease-path (long) attempts.
• Trace link appears when context exists; feature degrades gracefully when tracing is off.

References

Roadmap: docs/0.7-roadmap.md (WS-4, NEW-11). Related: #110, #143, ADR-023, ADR-026.