[frontend] - mplement End-to-End Encryption for Trade Chat Messages

[dark-sarge]

Location: server/src/routes/messages.ts, frontend/app/trades/[id]/chat/

Description

Buyers and sellers frequently need to coordinate delivery details (recipient phone numbers, network codes) during an active trade. Exchanging this sensitive information in plain server-stored messages is a privacy risk. An end-to-end encrypted trade chat using the Signal Protocol or NaCl box encryption is the appropriate solution.

Acceptance Criteria

• A /trades/[id]/chat page is accessible to both the buyer and seller of an active trade.
• Messages are encrypted client-side using the counterparty's Stellar public key (repurposed as a Curve25519 key) via NaCl box before being sent to the server.
• The server stores only the ciphertext and cannot decrypt messages — it acts purely as a relay.
• POST /api/trades/:id/messages (authenticated, buyer or seller only) stores an encrypted message.
• GET /api/trades/:id/messages returns ciphertexts, and the client decrypts them locally for display.
• Messages are automatically purged from the database 7 days after the trade reaches a terminal status (Completed, Cancelled).

[daameeloolaa-png]

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

Hi maintainer, I’d like to take this issue and work on it discreetly. I understand the responsibility and will ensure the fix is handled properly. Please assign it to me.

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

[NeduTheDev1]

@NeduTheDev1 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi maintainer please assign to me I can handle with no issues

ℹ️ Repo Maintainers: To accept this application, review their application or assign @NeduTheDev1 to this issue.

[Savitar-bot]

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

Hi, Maintainer I've studied the problem and am aware of the specifications. I'm sure I can manage it well. Please give it to me.

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