Let viewers set a per-streamer display name

Viewers can type a custom name shown to the streamer instead of
their Google account name. It's saved per (streamer, viewer) pair
in SQLite and pre-filled on future visits to the same send link.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

public/send.js

@@ -3,6 +3,7 @@ const mainSection = document.getElementById('hidden-until-login');
 const userPic = document.getElementById('user-pic');
 const userName = document.getElementById('user-name');
 const logoutBtn = document.getElementById('logout');
+const displayNameInput = document.getElementById('display-name');
 const messageInput = document.getElementById('message');
 const sendBtn = document.getElementById('send');
 const statusEl = document.getElementById('status');
@@ -22,6 +23,13 @@ function showLoggedOut() {
   mainSection.style.display = 'none';
 }
 
+async function loadDisplayName() {
+  const res = await fetch(`/api/viewer-name?token=${encodeURIComponent(token)}`);
+  if (!res.ok) return;
+  const { name } = await res.json();
+  displayNameInput.value = name || '';
+}
+
 async function handleCredentialResponse(response) {
   const res = await fetch('/auth/google', {
     method: 'POST',
@@ -32,6 +40,7 @@ async function handleCredentialResponse(response) {
   if (res.ok) {
     const { user } = await res.json();
     showLoggedIn(user);
+    loadDisplayName();
     // The socket connected before login with no session cookie; reconnect so
     // its handshake picks up the freshly-issued, now-authenticated cookie.
     socket.disconnect();
@@ -55,6 +64,7 @@ async function init() {
   const { user } = await meRes.json();
   if (user) {
     showLoggedIn(user);
+    loadDisplayName();
   } else {
     showLoggedOut();
   }
@@ -63,7 +73,8 @@ async function init() {
 sendBtn.addEventListener('click', () => {
   const text = messageInput.value.trim();
   if (!text) return;
-  socket.emit('send_message', { token, text });
+  const name = displayNameInput.value.trim();
+  socket.emit('send_message', { token, text, name });
   messageInput.value = '';
   statusEl.textContent = 'Отправлено';
   setTimeout(() => { statusEl.textContent = ''; }, 1500);