[server] - [frontend] - Implement Seller Rating System After Trade Completion

[dark-sarge]

Location: server/src/routes/ratings.ts, frontend/app/trades/[id]/rate/

Description

Buyers currently have no way to leave feedback after a trade. An off-chain rating system (1–5 stars + optional comment) stored in PostgreSQL complements the on-chain reputation score and gives future buyers richer seller information.

Acceptance Criteria

• A ratings table is created: id, trade_id (unique), reviewer_id, reviewee_id, stars (1–5), comment (varchar 300), created_at.
• POST /api/trades/:id/rate (authenticated, buyer only, trade must be Completed) accepts { stars: number, comment?: string } and creates a rating record.
• A rating can only be submitted once per trade — duplicates return HTTP 409.
• GET /api/users/:id/ratings returns a paginated list of ratings received by a user with their average star score.
• The trade detail page shows a "Rate this seller" CTA for 7 days after completion, then hides it.
• The seller's average rating and total review count are returned in GET /api/trades listing responses.

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[araoyeidris16-ctrl]

@araoyeidris16-ctrl has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

I will like to work on this field because I have the experience and I have seen the issue,it's something I can maintain

ℹ️ Repo Maintainers: To accept this application, review their application or assign @araoyeidris16-ctrl to this issue.