Fix UI review issues: accessibility, i18n, duplicate IDs, URL overflow

- Rename duplicate id="settings-error" to "device-settings-error"
- Add missing i18n key value_source.scene_sensitivity.hint (en/ru/zh)
- Add accessible label to password-toggle and Stop All buttons
- Add aria-hidden toggle on connection overlay
- Fix static image URL overflow with ellipsis truncation

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

server/src/wled_controller/templates/modals/device-settings.html

@@ -137,7 +137,7 @@
                     </div>
                 </div>
 
-                <div id="settings-error" class="error-message" style="display: none;"></div>
+                <div id="device-settings-error" class="error-message" style="display: none;"></div>
             </form>
         </div>
         <div class="modal-footer">