feat(i18n): force Spanish as the only language across all tenants

- i18n.js now locks currentLang to 'es' and overwrites pos_lang in localStorage.

- Disabled setLang language switching.

- Removed ES/EN toggle from sidebar.

- Bumped i18n.js and sidebar.js cache version on all templates.

pos/static/js/sidebar.js

@@ -15,7 +15,6 @@ window.renderSidebar = function(modulesOverride) {
     var initials = u.initials || '?';
     var currentPath = window.location.pathname;
     var currentTheme = localStorage.getItem('pos_theme') || 'industrial';
-    var currentLang = localStorage.getItem('pos_lang') || 'es';
 
     var modules = {};
     if (modulesOverride && typeof modulesOverride === 'object') {
@@ -104,16 +103,6 @@ window.renderSidebar = function(modulesOverride) {
         + '</button>'
         + '</div>';
 
-    // Language toggle buttons
-    var langHtml = '<div class="sidebar__lang-toggle">'
-        + '<button class="lang-toggle-btn' + (currentLang === 'es' ? ' is-active' : '') + '" onclick="setLang(\'es\')" title="Espanol">'
-        + '<span class="lang-flag">MX</span> ES'
-        + '</button>'
-        + '<button class="lang-toggle-btn' + (currentLang === 'en' ? ' is-active' : '') + '" onclick="setLang(\'en\')" title="English">'
-        + '<span class="lang-flag">US</span> EN'
-        + '</button>'
-        + '</div>';
-
     window.updateThemeButtons = function() {
         var t = localStorage.getItem('pos_theme') || 'industrial';
         document.querySelectorAll('.theme-toggle-btn').forEach(function(b, i) {
@@ -131,7 +120,6 @@ window.renderSidebar = function(modulesOverride) {
         + '</div>'
         + '<nav class="sidebar__nav">' + navHtml + '</nav>'
         + themeHtml
-        + langHtml
         + '<div class="sidebar__footer">'
         + '  <div class="sidebar__user-avatar">' + initials + '</div>'
         + '  <div class="sidebar__user-info">'