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/books.md

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+# `zappier-account-balance/books`
+
+**Package:** `zappier-account-balance`  
+**Source:** `packages/zappier-account-balance/src/books.js`  
+**Lines:** 90
+
+## What this module is
+
+Implementation module in `zappier-account-balance`. The tables below are extracted from the source (signatures + JSDoc).
+
+## Exports
+
+`AccountBooks`, `handle`
+
+## Types / interfaces / classes
+
+| Kind | Name |
+|------|------|
+| class | `AccountBooks` |
+
+## Functions
+
+| Name | Parameters | Param types (JSDoc) | Returns | Calls (same file / helpers) |
+|------|------------|---------------------|---------|-----------------------------|
+| `handle` | `subject, payload, books` | — | `unknown` | see Call graph |
+| `match` | `rows` | — | `unknown` | see Call graph |
+
+## Methods (class / object)
+
+| Name | Parameters |
+|------|------------|
+| `constructor` | `(none)` |
+| `prepaidCents` | `customerId` |
+| `adjust` | `{ customerId, cents, reason, agent, kind = 'credit' }` |
+| `recordUsage` | `entry` |
+| `recordPayment` | `entry` |
+| `statement` | `customerId` |
+
+## What it imports / requires
+
+_No imports detected._
+
+## Call graph (identifiers invoked)
+
+`constructor`, `prepaidCents`, `adjust`, `trunc`, `now`, `toString`, `random`, `slice`, `toISOString`, `unshift`, `recordUsage`, `recordPayment`, `statement`, `filter`, `match`, `handle`, `endsWith`
+
+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`.
+