Test: TS-07 returning user with existing display_name skips set-name

Inverse coverage for the auth path: TS-01..TS-06 all wipe the customer
row (drop_customer=true) so every OTP path lands on the new-user
set-name branch. TS-07 instead seeds an existing identified customer
(phone + display_name + is_anonymous=false) and verifies the OTP
sign-in returns the existing row unchanged via
resolveCustomerForIdentity branch 1, so /auth/set-name is never shown.

Adds:
* /internal/_test/seed-customer endpoint — upserts a customer with
  phone + display_name + is_anonymous=false.
* client_app/.maestro/scripts/seed_customer.js helper.
* client_app/.maestro/flows/ts-07_returning_existing_name_skips_setname.yaml.
* TS-07 scenario doc + coverage-map row in
  requirement/phase4-customer-flow.md.

The flow asserts the "halo, <name>" greeting on the returning-user home
variant (identified users always land on _SHomeReturningView regardless
of chat history) plus an explicit notVisible on "Siapa namamu" as a
belt-and-braces check.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

client_app/.maestro/scripts/seed_customer.js

@@ -0,0 +1,20 @@
+// Upsert a customer row with TEST_PHONE + DISPLAY_NAME via the dev-only
+// /internal/_test/seed-customer endpoint. Used by TS-07 to set up the
+// "returning user already has a name" precondition, so the OTP sign-in
+// path can verify the set-name screen is skipped for existing identified
+// customers.
+const phone = TEST_PHONE
+const displayName = DISPLAY_NAME
+const url = BACKEND_INTERNAL_URL || 'http://localhost:3001'
+if (!phone) throw new Error('TEST_PHONE env not set')
+if (!displayName) throw new Error('DISPLAY_NAME env not set')
+const resp = http.post(`${url}/internal/_test/seed-customer`, {
+  body: JSON.stringify({ phone, display_name: displayName }),
+  headers: { 'Content-Type': 'application/json' },
+})
+if (resp.status !== 200) {
+  throw new Error(`seed-customer failed (${resp.status}): ${resp.body}`)
+}
+const data = json(resp.body)
+output.CUSTOMER_ID = data.id
+output.CUSTOMER_DISPLAY_NAME = data.display_name