feat(collect): remove power-on/off, add skip-hung for Redfish collection

Remove power-on and power-off functionality from the Redfish collector;
keep host power-state detection and show a warning in the UI when the
host is powered off before collection starts.

Add a "Пропустить зависшие" (skip hung) button that lets the user abort
stuck Redfish collection phases without losing already-collected data.
Introduces a two-level context model in Collect(): the outer job context
covers the full lifecycle including replay; an inner collectCtx covers
snapshot, prefetch, and plan-B phases only. Closing the skipCh cancels
collectCtx immediately — aborts all in-flight HTTP requests and exits
plan-B loops — then replay runs on whatever rawTree was collected.

Signal path: UI → POST /api/collect/{id}/skip → JobManager.SkipJob()
→ close(skipCh) → goroutine in Collect() → cancelCollect().

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/server/job_manager.go

@@ -175,6 +175,43 @@ func (m *JobManager) UpdateJobDebugInfo(id string, info *CollectDebugInfo) (*Job
 	return cloned, true
 }
 
+func (m *JobManager) AttachJobSkip(id string, skipFn func()) bool {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	job, ok := m.jobs[id]
+	if !ok || job == nil || isTerminalCollectStatus(job.Status) {
+		return false
+	}
+	job.skipFn = skipFn
+	return true
+}
+
+func (m *JobManager) SkipJob(id string) (*Job, bool) {
+	m.mu.Lock()
+	job, ok := m.jobs[id]
+	if !ok || job == nil {
+		m.mu.Unlock()
+		return nil, false
+	}
+	if isTerminalCollectStatus(job.Status) {
+		cloned := cloneJob(job)
+		m.mu.Unlock()
+		return cloned, true
+	}
+	skipFn := job.skipFn
+	job.skipFn = nil
+	job.UpdatedAt = time.Now().UTC()
+	job.Logs = append(job.Logs, formatCollectLogLine(job.UpdatedAt, "Пропуск зависших запросов по команде пользователя"))
+	cloned := cloneJob(job)
+	m.mu.Unlock()
+
+	if skipFn != nil {
+		skipFn()
+	}
+	return cloned, true
+}
+
 func (m *JobManager) AttachJobCancel(id string, cancelFn context.CancelFunc) bool {
 	m.mu.Lock()
 	defer m.mu.Unlock()
@@ -229,5 +266,6 @@ func cloneJob(job *Job) *Job {
 	cloned.CurrentPhase = job.CurrentPhase
 	cloned.ETASeconds = job.ETASeconds
 	cloned.cancel = nil
+	cloned.skipFn = nil
 	return &cloned
 }