Fix auth: auto-create customer, display name flow, OTP auto-verify

- Backend: getOrCreateCustomer with phone fallback for re-login
- Backend: PATCH /api/client/auth/profile for display name update
- Client app: AuthNeedsDisplayNameData state + SetDisplayNameScreen
- Client app: ApiClient.patch method
- Both apps: handle verificationCompleted for auto-verify (test numbers)
- Both apps: skip credential sign-in if already auto-verified
- Remove debug prints from mitra auth + OTP screens
- Fix ChatRequestNotifier.startListening skips when accepting

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/src/services/customer.service.js

@@ -48,3 +48,40 @@ export const getCustomerByFirebaseUid = async (firebase_uid) => {
   `
   return customer
 }
+
+export const getOrCreateCustomer = async ({ firebase_uid, phone, display_name }) => {
+  // Return existing customer if already linked to this Firebase UID
+  const existing = await getCustomerByFirebaseUid(firebase_uid)
+  if (existing) return existing
+
+  // Check if a customer with this phone already exists (re-login with new Firebase UID)
+  if (phone) {
+    const [byPhone] = await sql`
+      SELECT id, display_name, is_anonymous, phone, created_at
+      FROM customers WHERE phone = ${phone}
+    `
+    if (byPhone) {
+      // Link the new Firebase UID to the existing phone-based customer
+      await sql`UPDATE customers SET firebase_uid = ${firebase_uid} WHERE id = ${byPhone.id}`
+      return { ...byPhone, firebase_uid }
+    }
+  }
+
+  // Auto-create a registered (non-anonymous) customer for phone/social login
+  // display_name is null — user must set it on first login
+  const [customer] = await sql`
+    INSERT INTO customers (firebase_uid, phone, display_name, is_anonymous)
+    VALUES (${firebase_uid}, ${phone || null}, ${display_name || null}, false)
+    RETURNING id, display_name, is_anonymous, phone, created_at
+  `
+  return customer
+}
+
+export const updateCustomerDisplayName = async (customerId, displayName) => {
+  const [customer] = await sql`
+    UPDATE customers SET display_name = ${displayName}
+    WHERE id = ${customerId}
+    RETURNING id, display_name, is_anonymous, phone, created_at
+  `
+  return customer
+}