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/subjects.md

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+# `zappier-account-balance/subjects`
+
+**Package:** `zappier-account-balance`  
+**Source:** `packages/zappier-account-balance/src/subjects.js`  
+**Lines:** 11
+
+## What this module is
+
+Implementation module in `zappier-account-balance`. The tables below are extracted from the source (signatures + JSDoc).
+
+## Exports
+
+`SUBJECTS`
+
+## Types / interfaces / classes
+
+_None extracted._
+
+## Functions
+
+_No top-level functions extracted._
+
+## What it imports / requires
+
+_No imports detected._
+
+## Call graph (identifiers invoked)
+
+_No local call identifiers extracted._
+
+## 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`.
+