refactor: P0 - remove testimonial, migrate footer & mobile menu to NAVIGATION_V2

- Remove TestimonialSection from homepage (no customers yet)
- Footer: dark theme, NAVIGATION_V2 + MEGA_DROPDOWN_DATA links
- Mobile Menu: NAVIGATION_V2 with collapsible dropdown support

src/app/(marketing)/home-content-v2.tsx

@@ -27,11 +27,6 @@ const ChallengeSection = dynamic(
   { loading: () => <SectionSkeleton />, ssr: false }
 );
 
-const TestimonialSection = dynamic(
-  () => import('@/components/sections/testimonial-section').then(mod => ({ default: mod.TestimonialSection })),
-  { loading: () => <SectionSkeleton />, ssr: false }
-);
-
 const CTASection = dynamic(
   () => import('@/components/sections/cta-section').then(mod => ({ default: mod.CTASection })),
   { loading: () => <SectionSkeleton />, ssr: false }
@@ -79,7 +74,6 @@ function HomeContentV2() {
       <SocialProofSection />
       <ProductMatrixSection />
       <ChallengeSection />
-      <TestimonialSection />
       <CTASection />
     </main>
   );