test(timeline): allow timeline package in entity-location ArchRule

The entities_reside_in_domain_packages ArchUnit rule has a hardcoded
allow-list of domain packages; add ..timeline.. so TimelineEvent passes.
CI caught this — the new domain package was not yet whitelisted.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

backend/src/test/java/org/raddatz/familienarchiv/shared/ArchitectureTest.java

@@ -122,7 +122,8 @@ class ArchitectureTest {
             .that().areAnnotatedWith(Entity.class)
             .should().resideInAnyPackage(
                 "..document..", "..person..", "..tag..", "..user..",
-                "..geschichte..", "..notification..", "..ocr..", "..audit.."
+                "..geschichte..", "..notification..", "..ocr..", "..audit..",
+                "..timeline.."
             );
 
     // TODO Rule 5: Controllers expose endpoints under their domain prefix