Fix navbar across all pages: add nav include, fonts, active state, spacing, stats, error pages

- Add nav.php include to 5 missing pages (cost-calculator, thank-you, 403, 404, 500)
- Add ErrorDocument directives to .htaccess for custom 403/404/500 pages
- Fix bogus accuracy stats (homepage, web-scraping, location pages)
- Fix invisible CTA buttons on property and financial service pages
- Add Google Fonts (Roboto Slab + Lato) to all pages missing it (tools, blog articles, error pages)
- Add active nav link highlighting (teal underline for current page)
- Improve footer contrast to WCAG AA, equal-height cards, mobile text scaling
- Consistent navbar-to-content spacing across all pages
- Bump cache version to v1.1.3

services/financial-data-services.php

@@ -402,7 +402,7 @@ $faqPageName = 'Financial Data Services FAQ';
             <div class="container">
                 <h1>Financial Data Services & Market Intelligence UK</h1>
                 <p class="hero-subtitle">FCA-aware financial data services for hedge funds, asset managers, and investment firms. Market data extraction, alternative data solutions, and compliant financial intelligence to support your investment strategies.</p>
-                <a href="/quote" class="btn btn-white">Request Consultation</a>
+                <a href="/quote" class="btn btn-primary">Request Consultation</a>
             </div>
         </section>