Wire zappier-edge into the live stack and add billing department APIs

Fleet now spawns the real zappier and middleware processes. Metered
timestamp/receipt/hash calls proxy to middleware when ZAPPIER_UPSTREAM
is set. CS credits, sales per-customer pricing, and QuickBooks export
are separate repos plugged into zappier-edge admin.

packages/zappier-customer-service/package.json

@@ -0,0 +1,11 @@
+{
+  "name": "zappier-customer-service",
+  "version": "0.1.0",
+  "private": true,
+  "type": "module",
+  "description": "Customer-service credits and notes; writes prepaid balances on zappier-edge",
+  "scripts": {
+    "start": "node src/server.js",
+    "test": "node --test test/*.test.js"
+  }
+}