feat(watchdog): separate watchdog from startup

- Add /api/v1/watchdog to enable/disable
- Scheduled task now runs every 15 minutes
- Use schtasks command line instead of XML
- Dashboard shows watchdog enabled state
- Preserve watchdog state during install

lib/openapi/spec_test.go

@@ -11,8 +11,8 @@ func TestSpec(t *testing.T) {
 	if !ok || len(paths) < 12 {
 		t.Fatalf("expected at least 12 paths, got %d", len(paths))
 	}
-	if _, ok := paths["/api/v1/status"]; !ok {
-		t.Fatal("missing /api/v1/status")
+	if _, ok := paths["/api/v1/watchdog"]; !ok {
+		t.Fatal("missing /api/v1/watchdog")
 	}
 	if _, ok := spec["security"]; !ok {
 		t.Fatal("missing security")