Handle empty inputs in Redis and database operations, improve safety seal validation, and enhance related tests

- Return empty arrays for empty inputs in Redis `mget`, `db_object_t`, and `users_o` operations.
- Refactor safety seal validation logic to handle numeric strings and improve clarity.
- Add unit and API tests to verify handling of empty inputs and numeric safety seal strings.

services/nginx/app/classes/redis.php

@@ -471,6 +471,10 @@ class redis implements redis_i
 
     public function mget(array $array_map): array
     {
+        if (empty($array_map)) {
+            return [];
+        }
+
         // Get multiple keys from Redis
         return $this->redis->mget($array_map);
     }