feat: add auto-update system with release checking, notification UI, and install-type-aware apply

- Abstract ReleaseProvider interface (Gitea impl, swappable for GitHub/GitLab)
- Background UpdateService with periodic checks, debounce, dismissed version persistence
- Install type detection (installer/portable/docker/dev) with platform-aware asset matching
- Download with progress events, silent NSIS reinstall, portable ZIP/tarball swap scripts
- Version badge pulse animation, dismissible banner with icon buttons, Settings > Updates tab
- Single source of truth: pyproject.toml version via importlib.metadata, CI stamps tag with sed
- API: GET/POST status, check, dismiss, apply, GET/PUT settings
- i18n: en, ru, zh (27+ keys each)

server/src/wled_controller/static/js/app.ts

@@ -199,6 +199,11 @@ import {
     loadLogLevel, setLogLevel,
     saveExternalUrl, getBaseOrigin, loadExternalUrl,
 } from './features/settings.ts';
+import {
+    loadUpdateStatus, initUpdateListener, checkForUpdates,
+    loadUpdateSettings, saveUpdateSettings, dismissUpdate,
+    initUpdateSettingsPanel, applyUpdate,
+} from './features/update.ts';
 
 // ─── Register all HTML onclick / onchange / onfocus globals ───
 
@@ -560,6 +565,14 @@ Object.assign(window, {
     saveExternalUrl,
     getBaseOrigin,
 
+    // update
+    checkForUpdates,
+    loadUpdateSettings,
+    saveUpdateSettings,
+    dismissUpdate,
+    initUpdateSettingsPanel,
+    applyUpdate,
+
     // appearance
     applyStylePreset,
     applyBgEffect,
@@ -703,6 +716,10 @@ document.addEventListener('DOMContentLoaded', async () => {
     startEntityEventListeners();
     startAutoRefresh();
 
+    // Initialize update checker (banner + WS listener)
+    initUpdateListener();
+    loadUpdateStatus();
+
     // Show getting-started tutorial on first visit
     if (!localStorage.getItem('tour_completed')) {
         setTimeout(() => startGettingStartedTutorial(), 600);