fix: XSS escaping, null guards, JS bug fixes, and documentation updates

- Escape $serverObject and $systemUrl in AdminHTML.php heredocs to prevent XSS
- Add null guard in Database::getSystemUrl() to prevent fatal error
- Guard primaryNetwork access in module.js to prevent null dereference
- Reset badge/traffic-bar CSS classes on refresh to prevent accumulation
- Add VNC popup-blocked check with user-facing message
- Add BS3 input-group-btn dual class for theme compatibility
- Escape billing template variables with |escape:'htmlall'
- Add cache-busting to admin CSS/JS includes
- Switch cache-busting format from version to date-based (20260207)
- Create .releaserc.json for automated CHANGELOG.md management
- Add changelog/git plugins to semantic-release workflow
- Remove manual [Unreleased] section from CHANGELOG.md
- Update README: install/upgrade with rsync, accuracy fixes, add keygen.js
- Update CLAUDE.md: add keygen.js, document removed features
- Fix SECURITY.md grammar and version operator

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

modules/servers/VirtFusionDirect/hooks.php

@@ -139,7 +139,7 @@ add_hook('ClientAreaFooterOutput', 1, function ($vars) {
         $systemUrl = Database::getSystemUrl();
 
         return "
-    <script src=\"" . htmlspecialchars($systemUrl, ENT_QUOTES, 'UTF-8') . "modules/servers/VirtFusionDirect/templates/js/keygen.js?v=0.0.20\"></script>
+    <script src=\"" . htmlspecialchars($systemUrl, ENT_QUOTES, 'UTF-8') . "modules/servers/VirtFusionDirect/templates/js/keygen.js?v=20260207\"></script>
     <script>
     document.addEventListener('DOMContentLoaded', function() {
         var osTemplates = " . json_encode($dropdownOptions, JSON_THROW_ON_ERROR | JSON_HEX_TAG | JSON_HEX_AMP | JSON_HEX_APOS | JSON_HEX_QUOT) . ";