[Feature] Add error state and timeout handling for asset data loading failures

[numbers-official]

Summary

When API calls fail during modal opening, the widget remains in a permanent shimmer/loading skeleton state with no error feedback, no timeout, and no way for consumers to detect the failure.

Location

File: src/modal/modal-manager.ts — Lines 47-62
File: src/asset/asset-service.ts — Lines 67-70, 89-92, 117-120

Problem

When the modal opens, ModalManager.updateModal() fires three parallel API calls (fetchAsset, hasNftProduct, fetchAssetMetadata). Each function catches all errors and silently returns undefined or false.

When fetchAsset returns undefined:

• updateModalAsset silently bails out (line 90: if (!assetModel) return)
• _assetLoaded never becomes true
• The modal stays in shimmer skeleton state indefinitely

This affects:

• Network failures (offline, DNS, timeouts)
• API downtime (500, 503 errors)
• Invalid nid values (404 responses)
• Rate limiting (429 responses)

Impact

• User experience: Users see an eternally-loading widget with no explanation and no call to action
• Developer experience: No programmatic way to detect failure — no error event, no rejected promise, no error state property
• Debugging: Errors only appear in console.error, invisible to end users and site operators

Suggested Implementation

1. Add _loadError state to CaptureEyeModal:

   @state() protected _loadError = false;

   When set, render a user-friendly message (e.g., "Unable to load provenance data") instead of the shimmer skeleton.

2. Add timeout in ModalManager.updateModal(): if fetchAsset does not resolve within 10 seconds, set the error state.

3. Dispatch custom error event from <capture-eye>:

   this.dispatchEvent(new CustomEvent('capture-eye-error', {
       detail: { nid: this.nid, error: 'Failed to load asset data' },
       bubbles: true,
       composed: true
   }));

4. Expose loading state property on <capture-eye> (loadingState: 'loading' | 'loaded' | 'error') for programmatic access.

5. Optional single retry with 2-3 second backoff for transient failures.