[Milestone 4] REST API & Query Layer

[Patrick-Ehimen]

Parent Issue #34

Goal

Expose indexed data through a REST API with filtering, tracing, and analytics.

Tasks

• HTTP server (chi or echo) with graceful shutdown
• GET /messages/{message_id} — full message details
• GET /messages — filter by src_chain, dst_chain, protocol, status, sender, receiver, time range; cursor pagination
• GET /transactions/{tx_hash}/messages — messages in a transaction
• GET /address/{address}/history — cross-chain history for an address
• GET /trace/{message_id} — full end-to-end event lifecycle
• GET /protocols/{protocol}/stats — volume, latency, success rate
• GET /routes/stats — top routes by volume
• GET /health — health check
• OpenAPI 3.0 spec
• Database indexes for query patterns
• API endpoint tests with seeded data

Acceptance Criteria

• All endpoints return correct data with working pagination and filters
• Trace endpoint returns full event lifecycle
• API responds within 500ms for single lookups