v0.6.0 - Service-level connectivity tracking + passive failure-report endpoint

connectivity.py:
- Generalized 'spark' subject to any string; renamed 'spark' field to 'subject'
- Legacy v0.5 events with the old 'spark' field are migrated transparently on read (kind defaults to 'transition')
- New record_report(subject, ok, source, detail, latency_ms): always appends an event with kind='report'; does NOT mutate the current state (only active polling is authoritative)
- summary() returns events normalized to the new schema

Wiring:
- /api/status now calls record_state for vllm/parakeet/magpie (dedup on no-change)
- /api/services calls record_state for each service after its http check
- Result: dashboard observes service-level transitions automatically with no extra polling

Passive endpoint:
- POST /api/health-event with {service, ok, source?, error?, ms?}
- Useful for external apps (e.g. Open WebUI) to surface sub-poll-interval failures the dashboard would otherwise miss

UI:
- Connectivity dialog groups events by subject (hosts ordered first, then services)
- Per-subject summary shows transition count, down count, report count, failed-report count
- Transitions and reports render inline with distinct styling; reports show source app + error + latency
- Legacy v0.5 events render unchanged

Docs:
- README documents /api/health-event with a curl example

Package: bump to 0.6.0:0

image/app/static/style.css

@@ -411,6 +411,8 @@ main {
 .conn-event .what { flex: 1; }
 .conn-event.up .what { color: var(--accent); }
 .conn-event.down .what { color: var(--error); }
+.conn-event.report .what { font-style: italic; }
+.conn-event .muted { color: var(--muted); font-style: normal; }
 .conn-event .dur { color: var(--muted); }
 .conn-summary { color: var(--muted); font-size: 11px; padding: 4px 0 10px; }
 .hw-metric { display: flex; align-items: center; gap: 10px; font-size: 12px; }