Cryplo Bridge: Deposit (ExCoin → Cryplo USD)

[MrCrystal2]

Parent PRD

Source: plans/cryplo-bridge.md — ExSize ↔ Cryplo Bridge

What to build

Implement deposit transfers so authenticated Cryplo users can convert ExCoin to USD in Cryplo.

End-to-end: Cryplo calls POST /api/cryplo/deposit with Bearer token + amount_usd + cryplo_user_id → ExSize verifies token → checks ExBucks balance (amount_usd / 2 = excoin_amount) → deducts ExBucks → records transfer in cryplo_transfers → returns success with new balance.

Also includes GET /api/cryplo/balance for Cryplo to check a user's ExCoin balance.

This includes:

• New cryplo_transfers table (id, exsize_user_id, type, amount_usd, excoin_amount, status, cryplo_tx_id, created_at, completed_at)
• POST /api/cryplo/deposit — deducts ExBucks, records transfer
• GET /api/cryplo/balance — returns current ExBucks balance
• All endpoints require Bearer token auth (API token from Cryplo Bridge: API Token Infrastructure + SSO Verify #56)

Acceptance criteria

• cryplo_transfers table created with proper indexes
• POST /api/cryplo/deposit deducts ExBucks from user (1 ExCoin = 2 USD)
• Returns 400 with insufficient_funds if balance too low
• Transfer recorded in cryplo_transfers with status 'completed'
• GET /api/cryplo/balance returns {excoin_balance, user_id} for authenticated user
• All endpoints require valid API token (401 without)
• Tests pass with uv run pytest tests/ -x

Blocked by

• Cryplo Bridge: API Token Infrastructure + SSO Verify #56 (API Token Infrastructure + SSO Verify — needed for token auth)

User stories addressed

• Deposit transfer (ExCoin → Cryplo USD)
• Balance check endpoint