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/store/lockfile_windows.go

@@ -0,0 +1,30 @@
+//go:build windows
+
+package store
+
+import (
+	"golang.org/x/sys/windows"
+)
+
+// processAlive returns true when the given PID is currently held by a
+// running Windows process. OpenProcess with PROCESS_QUERY_LIMITED_INFORMATION
+// is the supported way to check liveness without elevation.
+func processAlive(pid int) bool {
+	if pid <= 0 {
+		return false
+	}
+	h, err := windows.OpenProcess(windows.PROCESS_QUERY_LIMITED_INFORMATION, false, uint32(pid))
+	if err != nil {
+		return false
+	}
+	defer windows.CloseHandle(h)
+	var exitCode uint32
+	if err := windows.GetExitCodeProcess(h, &exitCode); err != nil {
+		// Conservative: if we can't ask, assume alive so we don't reclaim
+		// an active lock. Worst case the operator sees ErrLockHeld and
+		// removes the lockfile by hand.
+		return true
+	}
+	const stillActive = 259 // STILL_ACTIVE
+	return exitCode == stillActive
+}