Add GET /api/v1/requests/:id/history

[iexwr]

Context

Contributors and support need to see the event timeline for a request (created to paid/cancelled).

Acceptance criteria

• Returns an ordered JSON array of events for the request id: [{ type, at, data }].
• Source from a new Event table written by the indexer (add to Prisma schema).

Technical notes

• Order by ledger sequence / timestamp ascending.
• Reuse the event payloads the indexer already parses.

Testing

• Route test: create events via indexer fixture, assert /history returns them in order.