feat(payments): add Order & Escrow repository tests, prisma config, docs

Add 26 unit tests for PrismaOrderRepository and PrismaEscrowRepository
covering CRUD operations, pagination, domain mapping (bigint → Money),
idempotency key lookup, and escrow dispute workflow fields.

Update prisma.config.ts with dotenv import and seed command for Prisma 7.
Add architecture summary and codebase overview documentation files.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

prisma/prisma.config.ts

@@ -3,6 +3,8 @@ import { defineConfig } from 'prisma/config';
 
 // Use DATABASE_URL_DIRECT (bypasses PgBouncer) for migrations/introspection
 // when available; fall back to DATABASE_URL for local dev without PgBouncer.
+import 'dotenv/config';
+
 const databaseUrl =
   process.env.DATABASE_URL_DIRECT || process.env.DATABASE_URL!;
 
@@ -13,4 +15,8 @@ export default defineConfig({
   datasource: {
     url: databaseUrl,
   },
+  // Seed command — Prisma 7 reads this from config instead of package.json
+  migrations: {
+    seed: 'tsx prisma/seed.ts',
+  },
 });