feat(05-02): add application notification to providers

Add send_provider_application_notification() method:
- Hooks to frm_after_create_entry for job application form submissions
- Extracts applicant details (name, email, message) and job_id
- Fetches job details (title, location, type) from post and ACF fields
- Sends email to provider contact email (job_contact_email ACF field)
- Email includes full applicant info and job context
- Provider can reply directly to applicant email
- Error logging for missing contact email or wp_mail failures

Hook registered in setup_hooks() method

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

includes/class-notifications.php

@@ -22,6 +22,9 @@ class DDHH_JM_Notifications {
 
 		// Hook into post status transitions to detect job deactivations
 		add_action( 'transition_post_status', array( __CLASS__, 'send_admin_job_deactivation_notification' ), 10, 3 );
+
+		// Hook into Formidable form submissions to send application notifications
+		add_action( 'frm_after_create_entry', array( __CLASS__, 'send_provider_application_notification' ), 30, 2 );
 	}
 
 	/**
@@ -209,4 +212,127 @@ class DDHH_JM_Notifications {
 			);
 		}
 	}
+
+	/**
+	 * Send provider notification when a mentor applies to their job
+	 *
+	 * @param int $entry_id Entry ID.
+	 * @param int $form_id  Form ID.
+	 */
+	public static function send_provider_application_notification( $entry_id, $form_id ) {
+		// Only process job application form submissions
+		$application_form_id = DDHH_JM_Formidable::get_job_application_form_id();
+		if ( $form_id !== $application_form_id ) {
+			return;
+		}
+
+		// Get entry data
+		$entry = FrmEntry::getOne( $entry_id, true );
+		if ( ! $entry ) {
+			return;
+		}
+
+		// Extract field values
+		$applicant_name    = '';
+		$applicant_email   = '';
+		$applicant_message = '';
+		$job_id            = 0;
+
+		foreach ( $entry->metas as $field_id => $value ) {
+			$field = FrmField::getOne( $field_id );
+			if ( ! $field ) {
+				continue;
+			}
+
+			switch ( $field->field_key ) {
+				case 'applicant_name':
+					$applicant_name = sanitize_text_field( $value );
+					break;
+				case 'applicant_email':
+					$applicant_email = sanitize_email( $value );
+					break;
+				case 'applicant_message':
+					$applicant_message = sanitize_textarea_field( $value );
+					break;
+				case 'job_id':
+					$job_id = absint( $value );
+					break;
+			}
+		}
+
+		// Validate required fields
+		if ( empty( $applicant_name ) || empty( $applicant_email ) || empty( $applicant_message ) || empty( $job_id ) ) {
+			error_log( 'DDHH Job Manager: Missing required fields in job application submission' );
+			return;
+		}
+
+		// Get job post
+		$post = get_post( $job_id );
+		if ( ! $post || 'job_offer' !== $post->post_type ) {
+			error_log( sprintf( 'DDHH Job Manager: Invalid job_id %d in application submission', $job_id ) );
+			return;
+		}
+
+		// Get job details
+		$job_title    = $post->post_title;
+		$job_location = get_field( 'job_location', $job_id );
+		$job_type     = get_field( 'job_type', $job_id );
+
+		// Get provider contact email from ACF field
+		$provider_email = get_field( 'job_contact_email', $job_id );
+		if ( empty( $provider_email ) ) {
+			error_log(
+				sprintf(
+					'DDHH Job Manager: Cannot send application notification for job #%d - job_contact_email not set',
+					$job_id
+				)
+			);
+			return;
+		}
+
+		// Build email subject
+		$subject = sprintf( 'Neue Bewerbung für: %s', $job_title );
+
+		// Build email body
+		$body = sprintf(
+			"Sie haben eine neue Bewerbung für Ihr Stellenangebot erhalten.\n\n" .
+			"Stelle: %s\n" .
+			"Standort: %s\n" .
+			"Art: %s\n\n" .
+			"--- Bewerber ---\n" .
+			"Name: %s\n" .
+			"E-Mail: %s\n\n" .
+			"Nachricht:\n%s\n\n" .
+			"---\n" .
+			"Bitte antworten Sie direkt an %s.\n\n" .
+			"Diese E-Mail wurde automatisch gesendet.",
+			$job_title,
+			$job_location ? $job_location : 'Nicht angegeben',
+			$job_type ? $job_type : 'Nicht angegeben',
+			$applicant_name,
+			$applicant_email,
+			$applicant_message,
+			$applicant_email
+		);
+
+		// Set email headers
+		$headers = array( 'Content-Type: text/html; charset=UTF-8' );
+
+		// Convert plain text to HTML with line breaks
+		$html_body = nl2br( esc_html( $body ) );
+
+		// Send email
+		$sent = wp_mail( $provider_email, $subject, $html_body, $headers );
+
+		// Log if email fails
+		if ( ! $sent ) {
+			error_log(
+				sprintf(
+					'DDHH Job Manager: Failed to send application notification for job #%d "%s". Email may be disabled in Local WP environment.',
+					$job_id,
+					$job_title
+				)
+			);
+		}
+	}
 }