Fix NPE in CacheInvalidationFilter when request scope is unavailable

When a request is rejected before the Jersey injection scope is populated
(e.g. by ContentLengthLimitFilter), app.get() returns null instead of an
Optional, causing a NullPointerException in the response filter stage.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: namedgraph

src/main/java/com/atomgraph/linkeddatahub/server/filter/response/CacheInvalidationFilter.java

@@ -60,8 +60,9 @@ public class CacheInvalidationFilter implements ContainerResponseFilter
     @Override
     public void filter(ContainerRequestContext req, ContainerResponseContext resp) throws IOException
     {
-        // If no application was matched (e.g., non-existent dataspace), skip cache invalidation
-        if (!getApplication().isPresent()) return;
+        // If no application was matched (e.g., non-existent dataspace or request scope unavailable), skip cache invalidation
+        Optional<com.atomgraph.linkeddatahub.apps.model.Application> application = getApplication();
+        if (application == null || !application.isPresent()) return;
 
         if (req.getMethod().equals(HttpMethod.POST) && resp.getHeaderString(HttpHeaders.LOCATION) != null)
         {