feat(contact): add global WhatsApp FAB and mobile sticky CTA bar

- WhatsAppFab: 56px brand-green floating button (wa.me/919561417403), shown
  on every page; safe-area aware; lifts above the mobile CTA bar on <md.
- MobileStickyCtaBar: 3-column sticky bottom bar (Call / WhatsApp / Quote)
  visible only below the md breakpoint, with safe-area padding, 48px+ touch
  targets, and dark-mode-aware styling. Bottom spacer keeps the footer
  clear of the bar on mobile.
- Mounted both components globally via BaseLayout.
- Added tests/sticky-cta.spec.ts covering 360px and 1280px viewports,
  link integrity, no-overflow, hidden-at-md, and FAB/bar non-overlap.

src/layouts/BaseLayout.astro

@@ -6,6 +6,8 @@ import Header from '../components/Header.astro';
 import Footer from '../components/Footer.astro';
 import Analytics from '../components/Analytics.astro';
 import PWAInstallPrompt from '../components/PWAInstallPrompt.astro';
+import WhatsAppFab from '../components/WhatsAppFab.astro';
+import MobileStickyCtaBar from '../components/MobileStickyCtaBar.astro';
 import '../styles/global.css';
 
 interface Props {
@@ -290,6 +292,15 @@ const fullTitle = title === 'Home' ? siteName : `${title} | ${siteName}`;
     <!-- Footer -->
     <Footer />
 
+    <!-- Spacer to ensure footer/content clears the mobile sticky CTA bar (<md only) -->
+    <div aria-hidden="true" class="md:hidden h-[calc(64px+env(safe-area-inset-bottom,0px))] w-full"></div>
+
+    <!-- Mobile sticky bottom CTA bar (visible <md) -->
+    <MobileStickyCtaBar />
+
+    <!-- Floating WhatsApp action (global) -->
+    <WhatsAppFab />
+
     <!-- Scripts slot for page-specific scripts -->
     <slot name="scripts" />