Release version 1.1.13 - Critical class redeclaration fixes

Fixed critical class redeclaration errors affecting all plugin functionality
in version 1.1.12. All plugin component classes now properly guarded.

**CRITICAL FIXES:**
- Plugin completely non-functional in v1.1.12 (no settings, no frontend, no backend)
- Fatal errors for WC_TPP_Admin, WC_TPP_Product_Meta, WC_TPP_Frontend, WC_TPP_Cart, WC_TPP_Settings classes
- All classes now wrapped in class_exists() checks

**Files Modified:**
- includes/class-wc-tpp-admin.php
- includes/class-wc-tpp-product-meta.php
- includes/class-wc-tpp-frontend.php
- includes/class-wc-tpp-cart.php
- includes/class-wc-tpp-settings.php

**Technical Details:**
- Completes comprehensive redeclaration protection started in v1.1.9-1.1.12
- All 2 functions, 4 constants, and 6 classes now protected
- Plugin activates successfully and all features functional
- Settings page, product meta boxes, frontend display, cart integration all working

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

includes/class-wc-tpp-product-meta.php

@@ -7,7 +7,8 @@ if (!defined('ABSPATH')) {
     exit;
 }
 
-class WC_TPP_Product_Meta {
+if (!class_exists('WC_TPP_Product_Meta')) {
+    class WC_TPP_Product_Meta {
 
     public function __construct() {
         add_action('woocommerce_product_options_pricing', array($this, 'add_tier_pricing_fields'));
@@ -167,3 +168,4 @@ class WC_TPP_Product_Meta {
         update_post_meta($post_id, '_wc_tpp_restrict_to_packages', $restrict_to_packages);
     }
 }
+}