refactor: flatten src/AKSRT → src (drop theme-identifier dir)

Move all domain folders from src/AKSRT/{Domain} to src/{Domain}; remap
Composer PSR-4 "AKSRT\\": "src/"; update audit script + README + ADR
paths; remove dead tools/build-psr4-map.php (scanned deleted inc/classes).

src/Core/DBMigrator.php

@@ -0,0 +1,40 @@
+<?php
+/**
+ * @package AKSRT
+ */
+
+namespace AKSRT\Core;
+
+defined('ABSPATH') || exit;
+
+class DBMigrator {
+    use DBMigratorPart2;
+    use DBMigratorPart3;
+    use DBMigratorIdentity;
+
+    /** Current schema version; changing it re-runs dbDelta. */
+    const SCHEMA_VERSION = '1.17.0';
+
+    const OPT_KEY = 'aksrt_db_schema_version';
+
+    /**
+     * Register hooks.
+     */
+    public static function init(): void {
+        add_action('after_switch_theme', [self::class, 'maybe_migrate']);
+        add_action('admin_init', [self::class, 'maybe_migrate']);
+    }
+
+    /**
+     * Run table schema upgrade when version mismatches.
+     */
+    public static function maybe_migrate(): void {
+        $current = get_option(self::OPT_KEY, '');
+        if ($current === self::SCHEMA_VERSION) {
+            return;
+        }
+
+        self::run();
+        update_option(self::OPT_KEY, self::SCHEMA_VERSION);
+    }
+}