feat(apps): stepped creation wizard, branch previews, and app-creation fixes

This session (frontend focus):
- Rebuild /apps/new as a 4-step wizard (Basics → Configure → Trigger → Review):
  WizardRail, SourceKindPicker card grid, AppManifest review, per-step validation,
  ConfirmDialog-based unsaved-changes guard.
- Extract lib/workload/sourceForms.ts (single source of truth for source_config)
  + {Image,Compose,Static,Dockerfile}SourceForm + StaticDiscoveryWizard; fold the
  /apps/[id] edit form onto the same components (removes the duplication). Add
  vitest + sourceForms unit tests.
- Branch preview environments UI: /chain is_preview/preview_branch + a Preview
  environments panel on /apps/[id] (per-branch URLs, ConfirmDialog teardown, armed
  state); RegistryImagePicker on the registry trigger and the image source.
- Fixes: image-inspect 404 -> admin-gated POST /api/discovery/image/inspect;
  conflict-panel blur flicker; friendly localized discovery errors; CPU/Memory
  label hints; dashboard + /apps "Total workloads" count only source_kind workloads
  (drop stale trigger_kind gate); NPM cert/access-list name cache; EntityPicker
  empty-list guard.
- Update CLAUDE.md frontend conventions + add a Build & Test section.

Also captures pre-existing in-progress platform work (not from this session):
workload notifications, Prometheus metrics export, store lockfile, health probes,
backup hardening, and related store/webhook/scheduler changes.

internal/stats/collector.go

@@ -234,17 +234,17 @@ func (c *Collector) sampleAll(ctx context.Context, targets []target) []store.Con
 	found := make([]bool, len(targets))
 
 	var wg sync.WaitGroup
+loop:
 	for i, t := range targets {
 		// Acquire the semaphore in the parent loop so ctx cancellation
 		// short-circuits the queue rather than spawning goroutines that
-		// block on an unreachable slot.
+		// block on an unreachable slot. The labelled break exits the for
+		// loop directly; a bare `break` inside `select` would only break
+		// the select and let the loop continue.
 		select {
 		case sem <- struct{}{}:
 		case <-ctx.Done():
-			break
-		}
-		if ctx.Err() != nil {
-			break
+			break loop
 		}
 		wg.Add(1)
 		go func(i int, t target) {