Implement version 0.0.1 - Licensed Product type for WooCommerce

Add complete plugin infrastructure for selling software with license keys:

- New "Licensed Product" WooCommerce product type
- License key generation (XXXX-XXXX-XXXX-XXXX format) on order completion
- Domain-based license validation system
- REST API endpoints (validate, status, activate, deactivate)
- Customer My Account "Licenses" page
- Admin license management under WooCommerce > Licenses
- Checkout domain field for licensed products
- Custom database tables for licenses and product versions
- Twig template engine integration
- Full i18n support with German (de_CH) translation

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

assets/css/frontend.css

@@ -0,0 +1,124 @@
+/**
+ * WC Licensed Product - Frontend Styles
+ *
+ * @package Jeremias\WcLicensedProduct
+ */
+
+/* License Status Badges */
+.license-status {
+    display: inline-block;
+    padding: 0.25em 0.6em;
+    font-size: 0.85em;
+    font-weight: 600;
+    line-height: 1;
+    text-align: center;
+    white-space: nowrap;
+    vertical-align: baseline;
+    border-radius: 0.25rem;
+}
+
+.license-status-active {
+    background-color: #d4edda;
+    color: #155724;
+}
+
+.license-status-inactive {
+    background-color: #fff3cd;
+    color: #856404;
+}
+
+.license-status-expired {
+    background-color: #f8d7da;
+    color: #721c24;
+}
+
+.license-status-revoked {
+    background-color: #d6d8db;
+    color: #383d41;
+}
+
+/* License Table */
+.woocommerce-licenses-table {
+    width: 100%;
+    border-collapse: collapse;
+    margin-bottom: 1em;
+}
+
+.woocommerce-licenses-table th,
+.woocommerce-licenses-table td {
+    padding: 0.75em;
+    text-align: left;
+    border-bottom: 1px solid #e5e5e5;
+}
+
+.woocommerce-licenses-table th {
+    font-weight: 600;
+    background-color: #f8f8f8;
+}
+
+.woocommerce-licenses-table code {
+    font-family: monospace;
+    background-color: #f5f5f5;
+    padding: 0.2em 0.4em;
+    border-radius: 3px;
+    font-size: 0.9em;
+}
+
+/* Domain Field */
+#licensed-product-domain-field {
+    margin-top: 2em;
+    padding: 1.5em;
+    background-color: #f8f9fa;
+    border: 1px solid #e5e5e5;
+    border-radius: 4px;
+}
+
+#licensed-product-domain-field h3 {
+    margin-top: 0;
+    margin-bottom: 1em;
+    font-size: 1.1em;
+}
+
+#licensed-product-domain-field .description {
+    display: block;
+    margin-top: 0.5em;
+    font-size: 0.9em;
+    color: #666;
+}
+
+/* Responsive */
+@media screen and (max-width: 768px) {
+    .woocommerce-licenses-table,
+    .woocommerce-licenses-table thead,
+    .woocommerce-licenses-table tbody,
+    .woocommerce-licenses-table th,
+    .woocommerce-licenses-table td,
+    .woocommerce-licenses-table tr {
+        display: block;
+    }
+
+    .woocommerce-licenses-table thead tr {
+        position: absolute;
+        top: -9999px;
+        left: -9999px;
+    }
+
+    .woocommerce-licenses-table tr {
+        border: 1px solid #e5e5e5;
+        margin-bottom: 1em;
+    }
+
+    .woocommerce-licenses-table td {
+        border: none;
+        position: relative;
+        padding-left: 50%;
+    }
+
+    .woocommerce-licenses-table td:before {
+        content: attr(data-title);
+        position: absolute;
+        left: 0.75em;
+        width: 45%;
+        font-weight: 600;
+    }
+}