Decouple i18n from feature modules and fix auth/login UX

Replace hardcoded updateAllText() calls with languageChanged event
pattern so feature modules subscribe independently. Guard all API
calls behind apiKey checks to prevent unauthorized requests when not
logged in. Fix login modal localization, hide tabs when logged out,
clear all panels on logout, and treat profiles with no conditions as
always-true.

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

server/src/wled_controller/static/js/features/dashboard.js

@@ -593,6 +593,15 @@ export function stopUptimeTimer() {
     _stopUptimeTimer();
 }
 
+// Re-render dashboard when language changes
+document.addEventListener('languageChanged', () => {
+    if (!apiKey) return;
+    // Force perf section rebuild with new locale
+    const perfEl = document.querySelector('.dashboard-perf-persistent');
+    if (perfEl) perfEl.remove();
+    loadDashboard();
+});
+
 export function stopDashboardWS() {
     if (_dashboardWS) {
         _dashboardWS.close();