Add licensed variable product support for duration-based licenses (v0.5.3)

Customers can now purchase licenses with different durations (monthly,
yearly, lifetime) through WooCommerce product variations. Each variation
can have its own license validity settings.

New features:
- LicensedVariableProduct class for variable licensed products
- LicensedProductVariation class for individual variations
- Per-variation license duration and max activations settings
- Duration labels in checkout (Monthly, Quarterly, Yearly, etc.)
- Full support for WooCommerce Blocks checkout with variations
- Updated translations for German (de_CH)

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

src/Product/LicensedVariableProduct.php

@@ -0,0 +1,151 @@
+<?php
+/**
+ * Licensed Variable Product Class
+ *
+ * @package Jeremias\WcLicensedProduct\Product
+ */
+
+declare(strict_types=1);
+
+namespace Jeremias\WcLicensedProduct\Product;
+
+use Jeremias\WcLicensedProduct\Admin\SettingsController;
+use WC_Product_Variable;
+
+/**
+ * Licensed Variable Product type extending WooCommerce Variable Product
+ *
+ * This allows selling license subscriptions with different durations
+ * (e.g., monthly, yearly, lifetime) as product variations.
+ */
+class LicensedVariableProduct extends WC_Product_Variable
+{
+    /**
+     * Product type
+     */
+    protected $product_type = 'licensed-variable';
+
+    /**
+     * Constructor
+     */
+    public function __construct($product = 0)
+    {
+        parent::__construct($product);
+    }
+
+    /**
+     * Get product type
+     */
+    public function get_type(): string
+    {
+        return 'licensed-variable';
+    }
+
+    /**
+     * Licensed products are always virtual
+     */
+    public function is_virtual(): bool
+    {
+        return true;
+    }
+
+    /**
+     * Licensed products are purchasable
+     */
+    public function is_purchasable(): bool
+    {
+        return $this->exists() && $this->get_price() !== '';
+    }
+
+    /**
+     * Get max activations for this product (parent default)
+     * Falls back to default settings if not set on product
+     */
+    public function get_max_activations(): int
+    {
+        $value = $this->get_meta('_licensed_max_activations', true);
+        if ($value !== '' && $value !== null) {
+            return max(1, (int) $value);
+        }
+        return SettingsController::getDefaultMaxActivations();
+    }
+
+    /**
+     * Check if product has custom max activations set
+     */
+    public function has_custom_max_activations(): bool
+    {
+        $value = $this->get_meta('_licensed_max_activations', true);
+        return $value !== '' && $value !== null;
+    }
+
+    /**
+     * Get validity days (parent default - variations override this)
+     * Falls back to default settings if not set on product
+     */
+    public function get_validity_days(): ?int
+    {
+        $value = $this->get_meta('_licensed_validity_days', true);
+        if ($value !== '' && $value !== null) {
+            return (int) $value > 0 ? (int) $value : null;
+        }
+        return SettingsController::getDefaultValidityDays();
+    }
+
+    /**
+     * Check if product has custom validity days set
+     */
+    public function has_custom_validity_days(): bool
+    {
+        $value = $this->get_meta('_licensed_validity_days', true);
+        return $value !== '' && $value !== null;
+    }
+
+    /**
+     * Check if license should be bound to major version
+     * Falls back to default settings if not set on product
+     */
+    public function is_bound_to_version(): bool
+    {
+        $value = $this->get_meta('_licensed_bind_to_version', true);
+        if ($value !== '' && $value !== null) {
+            return $value === 'yes';
+        }
+        return SettingsController::getDefaultBindToVersion();
+    }
+
+    /**
+     * Check if product has custom bind to version setting
+     */
+    public function has_custom_bind_to_version(): bool
+    {
+        $value = $this->get_meta('_licensed_bind_to_version', true);
+        return $value !== '' && $value !== null;
+    }
+
+    /**
+     * Get current software version (derived from latest product version)
+     */
+    public function get_current_version(): string
+    {
+        $versionManager = new VersionManager();
+        $latestVersion = $versionManager->getLatestVersion($this->get_id());
+
+        return $latestVersion ? $latestVersion->getVersion() : '';
+    }
+
+    /**
+     * Get major version number from version string
+     */
+    public function get_major_version(): int
+    {
+        $versionManager = new VersionManager();
+        $latestVersion = $versionManager->getLatestVersion($this->get_id());
+
+        if ($latestVersion) {
+            return $latestVersion->getMajorVersion();
+        }
+
+        return 1;
+    }
+}