fix(frontend): defer LoadingManager DOM initialization to resolve i18n warning

Delay DOM creation in LoadingManager constructor to first use time,
ensuring window.i18n is ready before translate() is called.

This eliminates the 'i18n not available' console warning during
module initialization while maintaining correct translations
for cancel button and loading status text.

static/js/managers/LoadingManager.js

@@ -8,6 +8,22 @@ export class LoadingManager {
             return LoadingManager.instance;
         }
 
+        // Delay DOM creation until first use to ensure i18n is ready
+        this._initialized = false;
+        this.overlay = null;
+        this.loadingContent = null;
+        this.progressBar = null;
+        this.statusText = null;
+        this.cancelButton = null;
+        this.onCancelCallback = null;
+        this.detailsContainer = null;
+
+        LoadingManager.instance = this;
+    }
+
+    _ensureInitialized() {
+        if (this._initialized) return;
+
         this.overlay = document.getElementById('loading-overlay');
 
         if (!this.overlay) {
@@ -53,7 +69,6 @@ export class LoadingManager {
             this.loadingContent.appendChild(this.cancelButton);
         }
 
-        this.onCancelCallback = null;
         this.cancelButton.onclick = () => {
             if (this.onCancelCallback) {
                 this.onCancelCallback();
@@ -62,12 +77,11 @@ export class LoadingManager {
             }
         };
 
-        this.detailsContainer = null; // Will be created when needed
-
-        LoadingManager.instance = this;
+        this._initialized = true;
     }
 
     show(message = 'Loading...', progress = 0) {
+        this._ensureInitialized();
         this.overlay.style.display = 'flex';
         this.setProgress(progress);
         this.setStatus(message);
@@ -77,21 +91,25 @@ export class LoadingManager {
     }
 
     hide() {
+        if (!this._initialized) return;
         this.overlay.style.display = 'none';
         this.reset();
         this.removeDetailsContainer();
     }
 
     setProgress(percent) {
+        if (!this._initialized) return;
         this.progressBar.style.width = `${percent}%`;
         this.progressBar.setAttribute('aria-valuenow', percent);
     }
 
     setStatus(message) {
+        if (!this._initialized) return;
         this.statusText.textContent = message;
     }
 
     reset() {
+        if (!this._initialized) return;
         this.setProgress(0);
         this.setStatus('');
         this.removeDetailsContainer();
@@ -100,6 +118,7 @@ export class LoadingManager {
     }
 
     showCancelButton(onCancel) {
+        this._ensureInitialized();
         if (this.cancelButton) {
             this.onCancelCallback = onCancel;
             this.cancelButton.style.display = 'flex';
@@ -109,6 +128,7 @@ export class LoadingManager {
     }
 
     hideCancelButton() {
+        if (!this._initialized) return;
         if (this.cancelButton) {
             this.cancelButton.style.display = 'none';
             this.onCancelCallback = null;
@@ -117,6 +137,7 @@ export class LoadingManager {
 
     // Create a details container for enhanced progress display
     createDetailsContainer() {
+        this._ensureInitialized();
         // Remove existing container if any
         this.removeDetailsContainer();
 
@@ -332,12 +353,14 @@ export class LoadingManager {
     }
 
     showSimpleLoading(message = 'Loading...') {
+        this._ensureInitialized();
         this.overlay.style.display = 'flex';
         this.progressBar.style.display = 'none';
         this.setStatus(message);
     }
 
     restoreProgressBar() {
+        if (!this._initialized) return;
         this.progressBar.style.display = 'block';
     }
 }