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/index.html

@@ -158,6 +158,12 @@
                             <option value="counterclockwise" data-i18n="calibration.direction.counterclockwise">Counterclockwise</option>
                         </select>
                     </div>
+
+                    <div class="form-group">
+                        <label for="cal-offset" data-i18n="calibration.offset">LED Offset:</label>
+                        <input type="number" id="cal-offset" min="0" value="0" oninput="updateCalibrationPreview()">
+                        <small style="color: #aaa; display: block; margin-top: 4px;" data-i18n="calibration.offset_hint">LEDs from LED 0 to start corner (along strip)</small>
+                    </div>
                 </div>
 
                 <!-- LED Counts per Edge -->