fix: prevent deleting registry entries that would create sequence gaps

Only the last entry in a company+year sequence can be deleted. Trying
to delete an earlier number (e.g. #2 when #3 exists) returns a 409
error with a Romanian message explaining the restriction.

Also routes UI deletes through the API (like create/update) so they
get proper audit logging and sequence recalculation.

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

src/modules/registratura/components/registratura-module.tsx

@@ -216,7 +216,12 @@ export function RegistraturaModule() {
   };
 
   const handleDelete = async (id: string) => {
-    await removeEntry(id);
+    try {
+      await removeEntry(id);
+    } catch (err) {
+      const msg = err instanceof Error ? err.message : "Eroare la ștergere";
+      alert(msg);
+    }
   };
 
   /** All closes go through the close dialog */