Version 1.3.1 - Switch to SecureLicenseClient with signature verification

- Upgraded from LicenseClient to SecureLicenseClient with HMAC-SHA256 response signature verification
- Added Server Secret configuration field for secure communication
- Added rate limit exception handling with retry time display
- Added signature verification error handling
- Added URL validation error handling (SSRF protection)
- Updated all translation files with new strings
- Compiled .mo files for all 7 language variants

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

languages/wc-tier-package-prices.pot

@@ -2,9 +2,9 @@
 # This file is distributed under the GPL v2 or later.
 msgid ""
 msgstr ""
-"Project-Id-Version: WooCommerce Tier and Package Prices 1.2.7\n"
+"Project-Id-Version: WooCommerce Tier and Package Prices 1.3.1\n"
 "Report-Msgid-Bugs-To: https://src.bundespruefstelle.ch/wc-tier-package-prices\n"
-"POT-Creation-Date: 2025-12-30 00:00+0000\n"
+"POT-Creation-Date: 2026-01-27 00:00+0000\n"
 "MIME-Version: 1.0\n"
 "Content-Type: text/plain; charset=UTF-8\n"
 "Content-Transfer-Encoding: 8bit\n"
@@ -332,11 +332,32 @@ msgid "Permission denied."
 msgstr ""
 
 #: includes/class-wc-tpp-settings.php
-msgid "License key and server URL are required."
+msgid "Server Secret"
 msgstr ""
 
 #: includes/class-wc-tpp-settings.php
-msgid "Please enter both license server URL and license key."
+msgid "The shared secret for secure communication with the license server."
+msgstr ""
+
+#: includes/class-wc-tpp-settings.php
+msgid "License key, server URL, and server secret are required."
+msgstr ""
+
+#: includes/class-wc-tpp-settings.php
+#. translators: %d: Number of seconds to wait
+msgid "Rate limit exceeded. Please try again in %d seconds."
+msgstr ""
+
+#: includes/class-wc-tpp-settings.php
+msgid "Response signature verification failed. Please check your server secret."
+msgstr ""
+
+#: includes/class-wc-tpp-settings.php
+msgid "An unexpected error occurred. Please try again."
+msgstr ""
+
+#: includes/class-wc-tpp-settings.php
+msgid "Please enter license server URL, license key, and server secret."
 msgstr ""
 
 #: includes/class-wc-tpp-settings.php