Move WLED config tips to footer, add Web UI link, move preview to calibration

- Move WLED Configuration tips from Add Device modal to page footer
- Add WLED Web UI link in footer (auto-populated with first device URL)
- Add WLED Web UI button (globe icon) to device card actions
- Move pixel preview button from device card to calibration modal footer
- Add en/ru i18n keys for new UI elements

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

server/src/wled_controller/static/index.html

@@ -56,6 +56,14 @@
 
         <footer class="app-footer">
             <div class="footer-content">
+                <p class="footer-tip">
+                    <strong><span data-i18n="devices.wled_config">WLED Configuration:</span></strong> <span data-i18n="devices.wled_note">Configure your WLED device (effects, segments, color order, power limits, etc.) using the</span>
+                    <a href="https://kno.wled.ge/" target="_blank" rel="noopener" data-i18n="devices.wled_link">official WLED app</a>
+                    <span data-i18n="devices.wled_note_or">or the built-in</span>
+                    <a href="#" class="wled-webui-link" data-i18n="devices.wled_webui_link">WLED Web UI</a>
+                    <span data-i18n="devices.wled_note_webui">(open your device's IP in a browser).</span>
+                    <span data-i18n="devices.wled_note2">This controller sends pixel color data and controls brightness per device.</span>
+                </p>
                 <p>
                     Created by <strong>Alexei Dolgolyov</strong>
                     • <a href="mailto:dolgolyov.alexei@gmail.com">dolgolyov.alexei@gmail.com</a>
@@ -148,6 +156,7 @@
                 <div id="calibration-error" class="error-message" style="display: none;"></div>
             </div>
             <div class="modal-footer">
+                <button class="btn btn-secondary" onclick="showPixelPreview(document.getElementById('calibration-device-id').value)" data-i18n="preview.button" style="margin-right: auto;">Preview</button>
                 <button class="btn btn-secondary" onclick="closeCalibrationModal()" data-i18n="calibration.button.cancel">Cancel</button>
                 <button class="btn btn-primary" onclick="saveCalibration()" data-i18n="calibration.button.save">Save</button>
             </div>
@@ -257,11 +266,6 @@
                 <h2 data-i18n="devices.add">Add New Device</h2>
             </div>
             <div class="modal-body">
-                <div class="info-banner" style="margin-bottom: 16px; padding: 12px; background: rgba(33, 150, 243, 0.1); border-left: 4px solid #2196F3; border-radius: 4px;">
-                    <strong><span data-i18n="devices.wled_config">WLED Configuration:</span></strong> <span data-i18n="devices.wled_note">Configure your WLED device (effects, segments, color order, power limits, etc.) using the</span>
-                    <a href="https://kno.wled.ge/" target="_blank" rel="noopener" style="color: #2196F3; text-decoration: underline;" data-i18n="devices.wled_link">official WLED app</a>.
-                    <span data-i18n="devices.wled_note2">This controller sends pixel color data and controls brightness per device.</span>
-                </div>
                 <form id="add-device-form">
                     <div class="form-group">
                         <label for="device-name" data-i18n="device.name">Device Name:</label>