Security Hardening & Vulnerability Fixes

🔧 What's Improved

Security Scan Results

All error-level security findings have been resolved:

• XSS Protection: Added DOMPurify sanitization for all user-generated content rendered in the app
• Input Validation: Added Zod schema validation to edge functions that were accepting unvalidated request bodies
• SQL Injection Prevention: Removed raw SQL execution patterns and replaced with parameterized queries
• CORS Hardening: Tightened allowed origins for edge function endpoints

SEO & Crawlability Improvements

• Updated sitemap-index.xml with 6 missing pages and corrected 3 paths
• Added Disallow: /oauth to robots.txt to prevent indexing of auth flows
• Fixed lastmod dates across all sitemap entries