[FEAT] Implement Reputation Scoring Engine with Sybil Resistance

[Rampop01]

Issue #54

[FEAT] Implement Reputation Scoring Engine with Sybil Resistance

🔴 Priority: High
Difficulty: Hard
Estimated Effort: 3-4 days
Relevant Files: src/modules/reputation/reputation.service.ts, src/jobs/calculateReputation.job.ts
Labels: core-logic, reputation, priority:high

Requirements

1. Trust Score Calculation

   • Everyone starts at 50. Implement time-decay logic (recent transactions weigh more heavily).
   • Successful escrow/swap: +1 point. Lost dispute: -15 points. Dispute raised: -5 points pending investigation.
   • Reward streak bonus of +5 for users with >10 consecutive successful transactions.

2. Sybil Resistance

   • Limit reputation gain between the same two parties to a maximum of 3 transactions.
   • Transactions under $20 USDC equivalent do NOT positively impact the Trust Score.
   • If a user's score drops below 20, automatically suspend their ability to create new listings.

3. Asynchronous Job

   • Create a BullMQ job CalculateReputationJob that triggers immediately when an escrow completes and runs an hourly sweep for active users.
   • Cache the resulting score in user_profiles for instant reads by the frontend.

4. Testing Requirements

   • Unit tests: Provide mocked transaction histories and assert the exact expected score output.
   • Sybil test: Feed 50 transactions between the same two users and assert the score barely increases after the 3rd transaction.

---