test(crm): integration harness + schema-shape regression net

Adds two pieces:

- __tests__/integration/helpers/crmDb.js — boots a temp-SQLite test
  DB by invoking every migrations/core/*.up() directly. Bypasses
  knex's Migrator because its exclusive write lock deadlocks
  001_init's nested initializeDatabase() call. ~1 second cold start.

- __tests__/integration/crmSchema.test.js — 36 assertions on the
  table + column layout after the consolidated CRM migration runs.
  Pins:
    - every CRM table present (quotes, contracts, invoices + the
      eight supporting tables)
    - deal_uuid columns on all three lineage tables (the column
      DocumentLineageCard joins on — drop it anywhere and the card
      silently returns partial data)
    - back-pointer FKs (converted_contract_id, source_contract_id,
      source_quote_id) — the exact columns that triggered the
      Postgres FK-ordering bug fixed earlier in this PR
    - Storno discriminator (kind, cancels_invoice_id, replaces_
      invoice_id) per feedback_storno_filter_everywhere
    - event time columns from migration 137

A full quote→contract→invoice lineage walk is deferred — quote
service's nextQuoteNumber() opens an inner transaction from inside
the createQuote outer transaction, which deadlocks SQLite's default
1-connection pool. Postgres dev DBs never see it. Either fix the
service to thread trx through, or run lineage tests against a real
Postgres in CI (mirror schema-drift.yml). Filed as separate work.

backend/__tests__/integration/helpers/crmDb.js

@@ -0,0 +1,121 @@
+/**
+ * Test harness for CRM integration tests.
+ *
+ * Boots a temp-SQLite database, runs every `migrations/core/*.up()`
+ * directly (bypassing knex's Migrator — its exclusive write lock
+ * deadlocks 001_init's nested `initializeDatabase()` call), and
+ * exposes a small helper for seeding the minimal row set that the
+ * quote/contract/invoice services need to operate.
+ *
+ * Usage:
+ *
+ *   const { bootCrmDb, seedMinimal } = require('./helpers/crmDb');
+ *
+ *   beforeAll(async () => {
+ *     ({ db, cleanup } = await bootCrmDb());
+ *     ({ adminId, customerId } = await seedMinimal(db));
+ *   });
+ *   afterAll(async () => { await cleanup(); });
+ */
+
+const fs = require('fs');
+const path = require('path');
+const os = require('os');
+const bcrypt = require('bcrypt');
+
+async function runCoreMigrations(db) {
+  await db.schema.createTable('migrations', (t) => {
+    t.increments('id').primary();
+    t.string('filename').unique().notNullable();
+    t.timestamp('applied_at').defaultTo(db.fn.now());
+  });
+
+  const coreDir = path.resolve(__dirname, '..', '..', '..', 'migrations', 'core');
+  const files = (await fs.promises.readdir(coreDir))
+    .filter((f) => f.endsWith('.js'))
+    .sort();
+
+  for (const f of files) {
+    const mod = require(path.join(coreDir, f));
+    if (typeof mod.up === 'function') {
+      await mod.up(db);
+    }
+    await db('migrations').insert({ filename: f });
+  }
+}
+
+/**
+ * Boot a clean test DB. Returns { db, cleanup, tmpDir }.
+ * Caller must invoke cleanup() in afterAll to release the SQLite file
+ * and the temp directory.
+ */
+async function bootCrmDb() {
+  const tmpDir = await fs.promises.mkdtemp(path.join(os.tmpdir(), 'picpeak-crm-'));
+  process.env.NODE_ENV = 'test';
+  process.env.TEST_DATABASE_PATH = path.join(tmpDir, 'crm.db');
+  process.env.STORAGE_PATH = path.join(tmpDir, 'storage');
+  await fs.promises.mkdir(process.env.STORAGE_PATH, { recursive: true });
+
+  // No jest.resetModules() — every service the test later requires
+  // must share THIS db instance. Two module copies on one SQLite file
+  // each open their own knex pool and the SQLite write lock deadlocks
+  // the second one acquiring a connection. Caller is responsible for
+  // setting TEST_DATABASE_PATH before the first require of db.js
+  // (which knexfile reads at module-init time); bootCrmDb only works
+  // when invoked before any service import.
+  const { db } = require('../../../src/database/db');
+
+  await runCoreMigrations(db);
+
+  return {
+    db,
+    tmpDir,
+    cleanup: async () => {
+      try { await db.destroy(); } catch (_) {}
+      try { await fs.promises.rm(tmpDir, { recursive: true, force: true }); } catch (_) {}
+    },
+  };
+}
+
+/**
+ * Seed the minimal row set that quote/contract/invoice services
+ * dereference on creation: an admin user, an active customer, a
+ * business_profile row, and the app_settings keys the services read.
+ *
+ * Returns the ids the caller will pass into service calls.
+ */
+async function seedMinimal(db) {
+  const passwordHash = await bcrypt.hash('test-pass', 4); // low rounds = fast
+
+  const adminInsert = await db('admin_users').insert({
+    username: 'tester', email: '[email protected]',
+    password_hash: passwordHash, must_change_password: false,
+    created_at: new Date(),
+  }).returning('id');
+  const adminId = adminInsert[0]?.id ?? adminInsert[0];
+
+  // business_profile is a singleton; the row is seeded by migration 107
+  // for fresh installs. Defensive: insert if missing.
+  const profile = await db('business_profile').first();
+  if (!profile) {
+    await db('business_profile').insert({
+      legal_name: 'Test Studio',
+      default_currency: 'CHF',
+      default_locale: 'de',
+    });
+  }
+
+  const customerInsert = await db('customer_accounts').insert({
+    email: '[email protected]',
+    display_name: 'Test Customer',
+    password_hash: passwordHash,
+    preferred_language: 'de',
+    is_active: 1,
+    created_at: new Date(),
+  }).returning('id');
+  const customerId = customerInsert[0]?.id ?? customerInsert[0];
+
+  return { adminId, customerId };
+}
+
+module.exports = { bootCrmDb, seedMinimal };