implement admin panel with login functionality and dashboard layout

backend/scheme.sql

@@ -12,6 +12,17 @@ CREATE TABLE `users` (
   UNIQUE KEY `username` (`username`)
 );
 
+CREATE TABLE `admins` (
+  `id` int NOT NULL AUTO_INCREMENT,
+  `username` varchar(100) NOT NULL,
+  `password` varchar(255) NOT NULL,
+  `first_name` varchar(255) NOT NULL,
+  `last_name` varchar(255) NOT NULL,
+  `entry_created_at` timestamp NULL DEFAULT CURRENT_TIMESTAMP,
+  PRIMARY KEY (`id`),
+  UNIQUE KEY `username` (`username`)
+);
+
 CREATE TABLE `loans` (
   `id` int NOT NULL AUTO_INCREMENT,
   `username` varchar(100) NOT NULL,