feat(industry): construct centered high-impact testimonial block

[noevidence1017]

Closes #309

Implements the centered, high-impact testimonial block for the industry page.

• Renders oversized quotation marks above a centered blockquote
• Displays the featured testimonial with author name, role, and company (Sarah Chen, VP of Operations, Meridian Logistics)
• Follows the Component -> Hook -> Service architecture: Testimonial.tsx -> useTestimonial -> testimonialService
• Data is fetched from /api/industry/testimonial (dev-only fixture route, matches the existing app/api/fleet/drivers pattern) rather than hardcoded in the component
• Loading skeleton and error/retry state included
• 4 unit tests covering loading, error, rendered content, and the service response shape

Typography uses Tailwind's serif/sans font pairing for the quote versus attribution; no brand-specific typeface was found configured elsewhere in the codebase to match against.

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