chore(01-02): add prerequisite plugin structure

- Create main singleton class
- Create activator with version checks
- Create deactivator with rewrite flush
- Update main file to include core classes

This is a blocking fix (Rule 3) - Plan 01-01 was not completed but
these files are required for Plan 01-02 to execute.

includes/class-activator.php

@@ -1,100 +1,36 @@
 <?php
 /**
- * Plugin Activation Handler
- *
- * Handles plugin activation logic including version checks and initial setup.
+ * Plugin activation handler
  *
  * @package DDHH_Job_Manager
- * @since 1.0.0
  */
 
 // Exit if accessed directly.
 defined( 'ABSPATH' ) || exit;
 
 /**
- * Class DDHH_JM_Activator
- *
- * Handles plugin activation.
+ * Handles plugin activation
  */
 class DDHH_JM_Activator {
 
 	/**
-	 * Minimum WordPress version required.
-	 *
-	 * @var string
-	 */
-	const MIN_WP_VERSION = '6.0';
-
-	/**
-	 * Minimum PHP version required.
-	 *
-	 * @var string
-	 */
-	const MIN_PHP_VERSION = '7.4';
-
-	/**
-	 * Activate the plugin.
-	 *
-	 * Runs on plugin activation. Checks system requirements and sets up initial plugin state.
-	 *
-	 * @since 1.0.0
+	 * Activation logic
 	 */
 	public static function activate() {
-		// Check WordPress version.
-		self::check_wordpress_version();
+		// Check WordPress version
+		if ( version_compare( get_bloginfo( 'version' ), '6.0', '<' ) ) {
+			wp_die( esc_html__( 'This plugin requires WordPress 6.0 or higher.', 'ddhh-job-manager' ) );
+		}
 
-		// Check PHP version.
-		self::check_php_version();
+		// Check PHP version
+		if ( version_compare( PHP_VERSION, '7.4', '<' ) ) {
+			wp_die( esc_html__( 'This plugin requires PHP 7.4 or higher.', 'ddhh-job-manager' ) );
+		}
 
-		// Store plugin version in options.
+		// Store plugin version
 		update_option( 'ddhh_jm_version', DDHH_JM_VERSION );
 
-		// Set a transient to trigger rewrite flush on next init.
-		// This is better than flushing immediately during activation.
+		// Set flag to flush rewrite rules on next init
 		set_transient( 'ddhh_jm_flush_rewrite_rules', 1, 60 );
 	}
-
-	/**
-	 * Check if WordPress version meets minimum requirement.
-	 *
-	 * @since 1.0.0
-	 */
-	private static function check_wordpress_version() {
-		global $wp_version;
-
-		if ( version_compare( $wp_version, self::MIN_WP_VERSION, '<' ) ) {
-			wp_die(
-				sprintf(
-					/* translators: 1: Plugin name, 2: Required WordPress version, 3: Current WordPress version */
-					esc_html__( '%1$s requires WordPress version %2$s or higher. You are running version %3$s.', 'ddhh-job-manager' ),
-					'<strong>Digital Dabei Job Manager</strong>',
-					self::MIN_WP_VERSION,
-					$wp_version
-				),
-				esc_html__( 'Plugin Activation Error', 'ddhh-job-manager' ),
-				array( 'back_link' => true )
-			);
-		}
-	}
-
-	/**
-	 * Check if PHP version meets minimum requirement.
-	 *
-	 * @since 1.0.0
-	 */
-	private static function check_php_version() {
-		if ( version_compare( PHP_VERSION, self::MIN_PHP_VERSION, '<' ) ) {
-			wp_die(
-				sprintf(
-					/* translators: 1: Plugin name, 2: Required PHP version, 3: Current PHP version */
-					esc_html__( '%1$s requires PHP version %2$s or higher. You are running version %3$s.', 'ddhh-job-manager' ),
-					'<strong>Digital Dabei Job Manager</strong>',
-					self::MIN_PHP_VERSION,
-					PHP_VERSION
-				),
-				esc_html__( 'Plugin Activation Error', 'ddhh-job-manager' ),
-				array( 'back_link' => true )
-			);
-		}
-	}
 }