Add NATS account-balance SoT and statement review for customers, CS, and sales

Internal billing now uses verae.billing.* request-reply and pubs. zappier-account-balance tracks prepaid, credits, usage, and payments. Portal, admin, CS, and sales all review the same statement. Independent Forgejo repos stay split via push-module-repos.

docs/modules/zappier-account-balance/server.md

@@ -0,0 +1,53 @@
+# `zappier-account-balance/server`
+
+**Package:** `zappier-account-balance`  
+**Source:** `packages/zappier-account-balance/src/server.js`  
+**Lines:** 93
+
+## What this module is
+
+Implementation module in `zappier-account-balance`. The tables below are extracted from the source (signatures + JSDoc).
+
+## Exports
+
+_No named `export` / `module.exports` keys detected._
+
+## Types / interfaces / classes
+
+_None extracted._
+
+## Functions
+
+| Name | Parameters | Param types (JSDoc) | Returns | Calls (same file / helpers) |
+|------|------------|---------------------|---------|-----------------------------|
+| `startNats` | `(none)` | — | `unknown` | see Call graph |
+| `readBody` | `req` | — | `unknown` | see Call graph |
+| `reply` | `sub, fn` | — | `unknown` | see Call graph |
+| `json` | `code, obj` | — | `unknown` | see Call graph |
+
+## Methods (class / object)
+
+| Name | Parameters |
+|------|------------|
+| `reply` | `nc.subscribe(SUBJECTS.STATEMENT_GET, { queue: SUBJECTS.QUEUE }` |
+| `reply` | `nc.subscribe(SUBJECTS.BALANCE_GET, { queue: SUBJECTS.QUEUE }` |
+| `reply` | `nc.subscribe(SUBJECTS.BALANCE_ADJUST, { queue: SUBJECTS.QUEUE }` |
+
+## What it imports / requires
+
+- `node:http`
+- `./books.js`
+- `./subjects.js`
+
+## Call graph (identifiers invoked)
+
+`startNats`, `import`, `connect`, `split`, `async`, `parse`, `decode`, `fn`, `respond`, `encode`, `stringify`, `reply`, `subscribe`, `handle`, `write`, `readBody`, `on`, `push`, `resolve`, `concat`, `toString`, `createServer`, `writeHead`, `end`, `json`, `match`, `statement`, `adjust`, `listen`
+
+Each identifier is a call site in this file. Follow the import list to see the defining module; open that module’s MD for parameter and return types.
+
+## Return values (how to read this)
+
+- HTTP route handlers return Express `res.json(...)` bodies (see route docs).
+- Zapier `perform` functions return a **single object** (creates) or an **array** (triggers/searches).
+- Pricing functions return integer **cents** on `Quote.totalCents`.
+