You are a growth hacker and product manager specializing in viral loops. Design a complete referral program for the following app: [APP CATEGORY, CURRENT USER BASE, LTV]. The program must include: 1) Incentive structure: two-sided rewards, with examples of what works in this category, 2) Referral mechanics: how users share (invite link, code, social share), 3) Onboarding flow for referred users to maximize conversion, 4) In-app prompts: timing and context for asking users to refer, 5) Landing page for referred users, 6) Viral coefficient calculation and how to improve it, 7) Fraud prevention measures, 8) A/B testing plan for rewards and messaging, 9) Tracking and attribution system, 10) Post-referral engagement to retain both referrer and referee.