Real JSON null for empty product feature; SSR warm-cache button and CLI

Ticket 0068-FE: ProductFeatureJsonRenderer returned json_encode(null), which headless passes on as the STRING null (it only decodes object/array-looking strings) and crashed the front end. It now returns an empty string and the TypoScript field sets ifEmptyReturnNull = 1, giving a real JSON null. No other renderer used the pattern. Ticket 0066-FE: SsrPurgeService::warm() posts to the node /__warm endpoint (derived from SSR_PURGE_ENDPOINT, same secret), exposed as a Warm cache button with confirmation in the VITEC SSR module, a Cache warming progress row fed by /__health, and the CLI vitec:ssr-warm [paths]. Warm runs are deliberately not written to the purge log. Verified: two-path run 2/2 done, affected page delivers productfeature null.

Co-Authored-By: Claude Fable 5.2 <noreply@anthropic.com>

packages/vitec/Configuration/Backend/Modules.php

@@ -147,6 +147,10 @@ return [
                 'target' => \Evomedien\Vitec\Controller\Backend\SsrController::class . '::purgeAction',
                 'methods' => ['POST'],
             ],
+            'warm' => [
+                'target' => \Evomedien\Vitec\Controller\Backend\SsrController::class . '::warmAction',
+                'methods' => ['POST'],
+            ],
         ],
     ],
 ];

packages/vitec/Configuration/Sets/Vitecset/setup.typoscript

@@ -77,6 +77,9 @@ tt_content {
                 fields {
                     productfeature = USER
                     productfeature.userFunc = Evomedien\Vitec\UserFunc\ProductFeatureJsonRenderer->render
+                    # No product selected/visible -> real JSON null, not
+                    # the string "null" (ticket 0068-FE).
+                    productfeature.ifEmptyReturnNull = 1
                 }
             }
         }