Comprehensive SEO and UI improvements across site

SEO Improvements:
- Add Twitter/OG meta tags to gdpr-compliance.php and terms-of-service.php
- Add author bios with E-E-A-T signals to all blog articles
- Add breadcrumb schema markup to key pages
- Create new service pages: price-monitoring.php, competitive-intelligence.php
- Create location pages: london.php, manchester.php, birmingham.php
- Update sitemap.xml with new pages

UI/CSS Improvements:
- Move testimonials section from inline styles to CSS classes
- Standardize hero gradients to #144784 → #179e83 across all pages
- Unify card border styles to border-left: 4px solid #179e83
- Fix CTA gradient direction consistency on location pages
- Standardize breadcrumb colors to #144784
- Replace all purple accent colors (#667eea, #764ba2) with brand colors
- Add CSS variables for brand consistency in main.css

Code Cleanup:
- Delete 6 emergency CSS fix files (button-emergency-fix.css, etc.)
- Remove related-articles-fix.css references from blog articles
- Consolidate styles into main.css

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

500.php

@@ -21,7 +21,7 @@ error_log('500 Error triggered: ' . date('Y-m-d H:i:s') . ' - IP: ' . $_SERVER['
             font-family: 'Arial', sans-serif;
             margin: 0;
             padding: 0;
-            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
+            background: linear-gradient(135deg, #144784 0%, #179e83 100%);
             color: white;
             min-height: 100vh;
             display: flex;