'image/gif';
        if (base64String.startsWith('UklGR')) return 'image/webp';
        // Add basic audio/video guesses if needed, though relying on entry.mimeType is better
        return 'application/octet-stream'; // Default for unknown
    }

    async function loadMediaCache() {
        try {
            const response = await fetch('/admin_api/multimodal-cache'); // UPDATED API ENDPOINT
            if (!response.ok) {
                throw new Error(`HTTP error! status: ${response.status}`)