feat: visual polish, nav login link, pricing badge fix, cursor fix, button contrast

- Hero mockup: enhanced 3D perspective and shadow
- Testimonials: illustrated SVG avatars
- Growth pricing card: visual prominence (scale, gradient, badge)
- Most Popular badge: repositioned to avoid overlapping heading
- Nav: added Log In link next to Start Free Trial
- Fixed btn-primary text colour on anchor tags (white on blue)
- Fixed cursor: default on all non-interactive elements
- Disabled user-select on non-form content to prevent text caret

public/robots.txt

@@ -0,0 +1,16 @@
+# TenderRadar - Robots.txt
+# https://tenderradar.co.uk/robots.txt
+
+User-agent: *
+Allow: /
+Disallow: /dashboard.html
+Disallow: /dashboard
+Disallow: /profile.html
+Disallow: /profile
+Disallow: /alerts.html
+Disallow: /alerts
+Disallow: /api/
+Disallow: /admin/
+
+# Sitemap location
+Sitemap: https://tenderradar.co.uk/sitemap.xml