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.

packages/zappier-account-balance/test/books.test.js

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+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { AccountBooks, handle } from '../src/books.js';
+import { SUBJECTS } from '../src/subjects.js';
+
+test('adjust credits prepaid and statement lists credits usage payments', () => {
+  const books = new AccountBooks();
+  handle(SUBJECTS.BALANCE_ADJUST, { customerId: 'c1', cents: 500, reason: 'goodwill', agent: 'cs' }, books);
+  handle(SUBJECTS.USAGE_RECORDED, { customerId: 'c1', endpointId: 'timestamp', cents: 4 }, books);
+  handle(SUBJECTS.PAYMENT_RECORDED, { customerId: 'c1', cents: 1000, reason: 'reload' }, books);
+  const st = handle(SUBJECTS.STATEMENT_GET, { customerId: 'c1' }, books);
+  assert.equal(st.prepaidCents, 1496);
+  assert.equal(st.credits[0].cents, 500);
+  assert.equal(st.usage[0].endpointId, 'timestamp');
+  assert.equal(st.payments[0].kind, 'payment');
+});

packages/zappier-account-balance/test/health.test.js

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+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { spawn } from 'node:child_process';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const root = path.join(path.dirname(fileURLToPath(import.meta.url)), '..');
+
+test('account-balance health and statement', async () => {
+  const port = 18010;
+  const child = spawn(process.execPath, ['src/server.js'], {
+    cwd: root,
+    env: { ...process.env, PORT: String(port) },
+    stdio: ['ignore', 'pipe', 'pipe'],
+  });
+  await new Promise((r) => setTimeout(r, 400));
+  try {
+    const h = await (await fetch(`http://127.0.0.1:${port}/health`)).json();
+    assert.equal(h.role, 'zappier-account-balance');
+    await fetch(`http://127.0.0.1:${port}/adjust`, {
+      method: 'POST',
+      headers: { 'content-type': 'application/json' },
+      body: JSON.stringify({ customerId: 'c1', cents: 200, reason: 'test' }),
+    });
+    const st = await (await fetch(`http://127.0.0.1:${port}/statement/c1`)).json();
+    assert.equal(st.prepaidCents, 200);
+  } finally {
+    child.kill('SIGTERM');
+  }
+});