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

locations/birmingham.php

@@ -427,7 +427,7 @@ $breadcrumbs = [
                     <span class="stat-label">Birmingham Clients</span>
                 </div>
                 <div class="stat">
-                    <span class="stat-number">99.8%</span>
+                    <span class="stat-number">99.5%</span>
                     <span class="stat-label">Accuracy Rate</span>
                 </div>
                 <div class="stat">

locations/london.php

@@ -427,7 +427,7 @@ $breadcrumbs = [
                     <span class="stat-label">London Clients</span>
                 </div>
                 <div class="stat">
-                    <span class="stat-number">99.8%</span>
+                    <span class="stat-number">99.5%</span>
                     <span class="stat-label">Accuracy Rate</span>
                 </div>
                 <div class="stat">

locations/manchester.php

@@ -427,7 +427,7 @@ $breadcrumbs = [
                     <span class="stat-label">Manchester Clients</span>
                 </div>
                 <div class="stat">
-                    <span class="stat-number">99.8%</span>
+                    <span class="stat-number">99.5%</span>
                     <span class="stat-label">Accuracy Rate</span>
                 </div>
                 <div class="stat">