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>

web/templates/index.html

@@ -80,15 +80,9 @@
                     </div>
                     <div id="api-connect-status" class="api-connect-status"></div>
                     <div id="api-probe-options" class="api-probe-options hidden">
-                        <label class="api-form-checkbox" for="api-power-on">
-                            <input id="api-power-on" name="power_on_if_host_off" type="checkbox">
-                            <span>Включить перед сбором</span>
-                        </label>
-                        <label class="api-form-checkbox" for="api-power-off">
-                            <input id="api-power-off" name="stop_host_after_collect" type="checkbox">
-                            <span>Выключить после сбора</span>
-                        </label>
-                        <div class="api-probe-options-separator"></div>
+                        <div id="api-host-off-warning" class="api-host-off-warning hidden">
+                            &#9888; Host выключен — данные инвентаря могут быть неполными
+                        </div>
                         <label class="api-form-checkbox" for="api-debug-payloads">
                             <input id="api-debug-payloads" name="debug_payloads" type="checkbox">
                             <span>Сбор расширенных метрик для отладки</span>
@@ -102,7 +96,10 @@
                 <section id="api-job-status" class="job-status hidden" aria-live="polite">
                     <div class="job-status-header">
                         <h4>Статус задачи сбора</h4>
-                        <button id="cancel-job-btn" type="button">Отменить</button>
+                        <div class="job-status-actions">
+                            <button id="skip-hung-btn" type="button" class="hidden" title="Прервать зависшие запросы и перейти к анализу собранных данных">Пропустить зависшие</button>
+                            <button id="cancel-job-btn" type="button">Отменить</button>
+                        </div>
                     </div>
                     <div class="job-status-meta">
                         <div><span class="meta-label">jobId:</span> <code id="job-id-value">-</code></div>