feat(02-03): create dashboard template with job listing table

- Created templates/provider-dashboard.php with:
  - User role check (ddhh_provider)
  - WP_Query for current user's job_offer posts
  - Table display with German column headings
  - Status badges (Veröffentlicht/Ausstehend/Entwurf)
  - Edit and View action links
  - Empty state message
  - Responsive CSS styling

- Created includes/class-dashboard.php with:
  - Template loader method
  - Shortcode registration [ddhh_provider_dashboard]
  - Output buffering for shortcode content

Dashboard queries only current user's posts with proper capability checking.

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

includes/class-dashboard.php

@@ -0,0 +1,57 @@
+<?php
+/**
+ * Provider Dashboard Class
+ *
+ * Handles dashboard template loading and shortcode registration
+ *
+ * @package DDHH_Job_Manager
+ */
+
+// Exit if accessed directly.
+defined( 'ABSPATH' ) || exit;
+
+/**
+ * Dashboard functionality
+ */
+class DDHH_JM_Dashboard {
+
+	/**
+	 * Initialize dashboard functionality
+	 */
+	public static function init() {
+		// Register shortcode
+		add_shortcode( 'ddhh_provider_dashboard', array( __CLASS__, 'render_shortcode' ) );
+	}
+
+	/**
+	 * Get template path
+	 *
+	 * @return string Path to dashboard template
+	 */
+	public static function get_template() {
+		return DDHH_JM_PLUGIN_DIR . 'templates/provider-dashboard.php';
+	}
+
+	/**
+	 * Render dashboard shortcode
+	 *
+	 * @return string Dashboard HTML output
+	 */
+	public static function render_shortcode() {
+		// Start output buffering
+		ob_start();
+
+		// Load template
+		$template_path = self::get_template();
+		if ( file_exists( $template_path ) ) {
+			load_template( $template_path, false );
+		} else {
+			echo '<div class="ddhh-error-message">';
+			echo '<p>Dashboard-Vorlage konnte nicht gefunden werden.</p>';
+			echo '</div>';
+		}
+
+		// Return buffered output
+		return ob_get_clean();
+	}
+}