fix(ns): root-qualify PHP builtins after PSR-4 move

Namespaced classes resolved DateTimeImmutable etc. under AKSRT\*
(e.g. Credits\DateTimeImmutable). Prefix with \ globally.

src/AKSRT/Credits/Earn.php

@@ -57,7 +57,7 @@ class Earn {
 		if ($user_id <= 0 || !class_exists('PointsFree')) {
 			return;
 		}
-		$today = (new DateTimeImmutable('today', wp_timezone()))->format('Y-m-d');
+		$today = (new \DateTimeImmutable('today', wp_timezone()))->format('Y-m-d');
 		$last  = (string) get_user_meta($user_id, PointsFree::META_LOGIN, true);
 		if ($last === $today) {
 			return;

src/AKSRT/Credits/Invite.php

@@ -238,7 +238,7 @@ class Invite {
         $log_table = \AKSRT\Core\DBMigrator::table('credit_log');
         if (!$log_table) return true;
 
-        $today_utc = (new DateTimeImmutable('today', wp_timezone()))->setTimezone(new DateTimeZone('UTC'))->format('Y-m-d H:i:s');
+        $today_utc = (new \DateTimeImmutable('today', wp_timezone()))->setTimezone(new \DateTimeZone('UTC'))->format('Y-m-d H:i:s');
         $count = (int) $wpdb->get_var($wpdb->prepare(
             "SELECT COUNT(*) FROM {$log_table} WHERE reason = 'invite' AND ip = %s AND created_at >= %s",
             $ip,

src/AKSRT/Credits/PointsFree.php

@@ -269,7 +269,7 @@ class PointsFree {
 	}
 
 	private static function today_key(): string {
-		return (new DateTimeImmutable('today', wp_timezone()))->format('Y-m-d');
+		return (new \DateTimeImmutable('today', wp_timezone()))->format('Y-m-d');
 	}
 
 	/**

src/AKSRT/Credits/Signin.php

@@ -153,7 +153,7 @@ class Signin {
 
     /** 站点时区下的今日日期 'Y-m-d' */
     private function today_date(): string {
-        return (new DateTimeImmutable('today', wp_timezone()))->format('Y-m-d');
+        return (new \DateTimeImmutable('today', wp_timezone()))->format('Y-m-d');
     }
 
     /** 取签到记录 */
@@ -181,7 +181,7 @@ class Signin {
         $table = \AKSRT\Core\DBMigrator::table('signin_log');
         if (!$table) return [];
 
-        $from_date = (new DateTimeImmutable("-{$days} days", wp_timezone()))->format('Y-m-d');
+        $from_date = (new \DateTimeImmutable("-{$days} days", wp_timezone()))->format('Y-m-d');
 
         $rows = $wpdb->get_results($wpdb->prepare(
             "SELECT signin_date FROM {$table} WHERE user_id = %d AND signin_date >= %s ORDER BY signin_date ASC",
@@ -209,19 +209,19 @@ class Signin {
         if (empty($rows)) return 0;
 
         $dates = array_map(fn($r) => $r['signin_date'], $rows);
-        $today = new DateTimeImmutable($today_str);
+        $today = new \DateTimeImmutable($today_str);
         $tz = wp_timezone();
 
         // 起点：若今天已签则从今天回看，否则从昨天回看
         $cursor = in_array($today_str, $dates, true)
             ? $today
-            : $today->sub(new DateInterval('P1D'));
+            : $today->sub(new \DateInterval('P1D'));
 
         $count = 0;
         foreach ($dates as $d) {
             if ($d === $cursor->format('Y-m-d')) {
                 $count++;
-                $cursor = $cursor->sub(new DateInterval('P1D'));
+                $cursor = $cursor->sub(new \DateInterval('P1D'));
             } else {
                 break;
             }