feat: Add payment API for fake Algora

[buildingvibes]

Summary

Implements a complete payment API for simulating bounty payments in fake Algora. This provides a mock payment system for testing bounty payment workflows.

Fixes #1

Features

Payment Management:

• Create payments with recipient, amount, and optional bounty metadata
• List payments with optional filters (recipient, status)
• Get payment by ID
• Complete/mark payments as successful

Database Schema:

• Added Payment model with fields:
  • payment_id: Unique identifier (auto-generated)
  • recipient: User receiving the payment
  • amount: Payment amount (positive number)
  • currency: Currency code (default: USD)
  • status: pending | completed | failed
  • bounty_id: Optional bounty identifier
  • issue_number: Optional GitHub issue number
  • repository: Optional repository name
  • created_at: Timestamp of creation
  • completed_at: Timestamp of completion

API Endpoints

POST /payments/create

Create a new payment.

Request:

{
  "recipient": "user123",
  "amount": 100,
  "currency": "USD",
  "bounty_id": "bounty_456",
  "issue_number": 123,
  "repository": "tscircuit/test-repo"
}

Response:

{
  "payment": {
    "payment_id": "pay_0",
    "recipient": "user123",
    "amount": 100,
    "currency": "USD",
    "status": "pending",
    "bounty_id": "bounty_456",
    "issue_number": 123,
    "repository": "tscircuit/test-repo",
    "created_at": "2026-02-09T18:00:00.000Z"
  }
}

GET /payments/list

List all payments with optional filters.

Query Parameters:

• recipient (optional): Filter by recipient
• status (optional): Filter by status (pending, completed, failed)

Response:

{
  "payments": [ ... ]
}

GET /payments/get

Get a specific payment by ID.

Query Parameters:

• payment_id (required): Payment ID

Response:

{
  "payment": { ... }
}

POST /payments/complete

Mark a payment as completed.

Request:

{
  "payment_id": "pay_0"
}

Response:

{
  "ok": true
}

Testing

Comprehensive test coverage for all endpoints:

• Payment creation with all fields
• Payment creation with minimal fields
• Listing all payments
• Filtering payments by recipient
• Completing payments and verifying status changes

Test Results:

bun test v1.3.9 (cf6cdbbb)

 7 pass
 0 fail
 20 expect() calls
Ran 7 tests across 5 files. [92.00ms]

Implementation Details

• Uses Zustand for state management
• Follows existing code patterns (winterspec, zod validation)
• Auto-incrementing payment IDs
• ISO timestamp generation for created_at and completed_at
• Type-safe implementation with TypeScript and Zod schemas

/claim #1