Add connection overlay and Gitea CI/CD workflow

Show full-screen overlay with spinner when server is unreachable,
with periodic health checks that auto-hide on reconnect.
Add Gitea Actions workflow for auto-deploy on release tags.

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

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

@@ -7,7 +7,7 @@ import { apiKey, setApiKey, refreshInterval } from './core/state.js';
 import { Modal } from './core/modal.js';
 
 // Layer 1: api, i18n
-import { loadServerInfo, loadDisplays, configureApiKey } from './core/api.js';
+import { loadServerInfo, loadDisplays, configureApiKey, startConnectionMonitor, stopConnectionMonitor } from './core/api.js';
 import { t, initLocale, changeLocale } from './core/i18n.js';
 
 // Layer 2: ui
@@ -506,6 +506,7 @@ window.addEventListener('beforeunload', () => {
     if (refreshInterval) {
         clearInterval(refreshInterval);
     }
+    stopConnectionMonitor();
     stopEventsWS();
     disconnectAllKCWebSockets();
     disconnectAllLedPreviewWS();
@@ -552,6 +553,10 @@ document.addEventListener('DOMContentLoaded', async () => {
     // Setup form handler
     document.getElementById('add-device-form').addEventListener('submit', handleAddDevice);
 
+    // Always monitor server connection (even before login)
+    loadServerInfo();
+    startConnectionMonitor();
+
     // Show modal if no API key is stored
     if (!apiKey) {
         setTimeout(() => {
@@ -563,7 +568,6 @@ document.addEventListener('DOMContentLoaded', async () => {
     }
 
     // User is logged in, load data
-    loadServerInfo();
     loadDisplays();
     loadTargetsTab();