Add proper HTML escaping for admin UI user data rendering, and eliminate all web lint issues closes #336 #338

[crivetimihai]

Add proper HTML escaping for admin UI user data rendering

Closes #336 closes #338

Changes

• Added escapeHtml() function that escapes HTML special characters
• Applied HTML escaping to all user data before rendering in modals and tables
• Implemented safe DOM manipulation using textContent for table cells
• Added safeUrl() helper for URL validation

Impact

• Ensures user input displays correctly as text content without unintended HTML rendering
• Improves data display consistency across admin UI components
• Applies proper output encoding throughout the interface

Testing

• Verified HTML content like <img src=x onerror="alert('test')"> is properly escaped and displayed as text
• Confirmed all user data displays correctly without breaking existing functionality

Additional Improvements to Consider

Immediate:

• Add Content Security Policy (CSP) headers for enhanced browser protection
• Implement server-side input validation
• Review file upload functionality for similar rendering issues
• Add automated testing for proper data escaping

Medium-term:

• Consider migrating to a dedicated sanitization library (e.g., DOMPurify)
• Add CSRF protection for form submissions
• Establish consistent data handling patterns across components