Add DDP protocol support, fix event loop blocking, and add LED offset calibration

- Add DDP client for LED strips >500 LEDs (UDP port 4048), with automatic
  fallback from HTTP JSON API when LED count exceeds limit
- Wrap blocking operations (screen capture, image processing) in
  asyncio.to_thread() to prevent event loop starvation
- Turn on WLED device and enable live mode when starting DDP streaming
- Add LED strip offset field to calibration (rotates color array to match
  physical LED position vs start corner)
- Add server management scripts (start, stop, restart, background start)
- Fix WebUI auth error handling and auto-refresh loop
- Add development API key to default config
- Add i18n translations for offset field (en/ru)

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

server/src/wled_controller/static/app.js

@@ -2,6 +2,9 @@ const API_BASE = '/api/v1';
 let refreshInterval = null;
 let apiKey = null;
 
+// Track logged errors to avoid console spam
+const loggedErrors = new Map(); // deviceId -> { errorCount, lastError }
+
 // Locale management
 let currentLocale = 'en';
 let translations = {};
@@ -181,6 +184,12 @@ function handle401Error() {
     localStorage.removeItem('wled_api_key');
     apiKey = null;
 
+    // Stop auto-refresh to prevent repeated 401 errors
+    if (refreshInterval) {
+        clearInterval(refreshInterval);
+        refreshInterval = null;
+    }
+
     if (typeof updateAuthUI === 'function') {
         updateAuthUI();
     }
@@ -392,8 +401,14 @@ async function loadDevices() {
                     });
                     const metrics = await metricsResponse.json();
 
-                    // Log device info, especially if there are errors
-                    if (metrics.errors_count > 0) {
+                    // Log device errors only when they change (avoid console spam)
+                    const deviceKey = device.id;
+                    const lastLogged = loggedErrors.get(deviceKey);
+                    const hasNewErrors = !lastLogged ||
+                                       lastLogged.errorCount !== metrics.errors_count ||
+                                       lastLogged.lastError !== metrics.last_error;
+
+                    if (metrics.errors_count > 0 && hasNewErrors) {
                         console.warn(`[Device: ${device.name || device.id}] Has ${metrics.errors_count} error(s)`);
 
                         // Log recent errors from state
@@ -412,6 +427,16 @@ async function loadDevices() {
                         // Log full state and metrics for debugging
                         console.log('Full state:', state);
                         console.log('Full metrics:', metrics);
+
+                        // Update tracking
+                        loggedErrors.set(deviceKey, {
+                            errorCount: metrics.errors_count,
+                            lastError: metrics.last_error
+                        });
+                    } else if (metrics.errors_count === 0 && lastLogged) {
+                        // Clear tracking when errors are resolved
+                        console.log(`[Device: ${device.name || device.id}] Errors cleared`);
+                        loggedErrors.delete(deviceKey);
                     }
 
                     return { ...device, state, metrics };
@@ -763,7 +788,10 @@ function startAutoRefresh() {
     }
 
     refreshInterval = setInterval(() => {
-        loadDevices();
+        // Only refresh if user is authenticated
+        if (apiKey) {
+            loadDevices();
+        }
     }, 2000); // Refresh every 2 seconds
 }
 
@@ -840,6 +868,7 @@ async function showCalibration(deviceId) {
         // Set layout
         document.getElementById('cal-start-position').value = calibration.start_position;
         document.getElementById('cal-layout').value = calibration.layout;
+        document.getElementById('cal-offset').value = calibration.offset || 0;
 
         // Set LED counts per edge
         const edgeCounts = { top: 0, right: 0, bottom: 0, left: 0 };
@@ -984,9 +1013,12 @@ async function saveCalibration() {
         }
     });
 
+    const offset = parseInt(document.getElementById('cal-offset').value || 0);
+
     const calibration = {
         layout: layout,
         start_position: startPosition,
+        offset: offset,
         segments: segments
     };