fix: correct Formidable API usage and move activation hooks to top level

- Replace non-existent FrmFormActionsController::create_action() with proper API
  - Use get_form_actions('wppost')->prepare_new() pattern
  - Affects job submission, edit, and deactivation forms
- Move register_activation_hook() to main plugin file top level
  - WordPress requires activation hooks at bootstrap, not in plugins_loaded
  - Fixes missing page creation on plugin activation

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

includes/class-ddhh-job-manager.php

@@ -43,10 +43,6 @@ class DDHH_JM_Job_Manager {
 	 * Initialize hooks
 	 */
 	private function init_hooks() {
-		// Register activation and deactivation hooks
-		register_activation_hook( DDHH_JM_PLUGIN_FILE, array( 'DDHH_JM_Activator', 'activate' ) );
-		register_deactivation_hook( DDHH_JM_PLUGIN_FILE, array( 'DDHH_JM_Deactivator', 'deactivate' ) );
-
 		// Initialize post types
 		add_action( 'init', array( 'DDHH_JM_Post_Types', 'register' ) );