Initial commit: overlay + sender pages for StreamLabs browser source

Express + Socket.IO backend with Google login on the sender page,
a transparent overlay page for OBS/StreamLabs Browser Source, and
TTS voice-over via the edge-tts Python CLI (same engine as
t2sTelegramBot). Dockerized for deployment.

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

public/sender.js

@@ -0,0 +1,86 @@
+const loginContainer = document.getElementById('login-container');
+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 messageInput = document.getElementById('message');
+const sendBtn = document.getElementById('send');
+const statusEl = document.getElementById('status');
+
+const socket = io();
+
+function showLoggedIn(user) {
+  loginContainer.style.display = 'none';
+  mainSection.style.display = 'block';
+  userPic.src = user.picture || '';
+  userName.textContent = user.name || user.email;
+}
+
+function showLoggedOut() {
+  loginContainer.style.display = 'block';
+  mainSection.style.display = 'none';
+}
+
+async function handleCredentialResponse(response) {
+  const res = await fetch('/auth/google', {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify({ credential: response.credential }),
+  });
+
+  if (res.ok) {
+    const { user } = await res.json();
+    showLoggedIn(user);
+    // The socket connected before login with no session cookie; reconnect so
+    // its handshake picks up the freshly-issued, now-authenticated cookie.
+    socket.disconnect();
+    socket.connect();
+  } else {
+    statusEl.textContent = 'Не удалось войти, попробуйте ещё раз';
+  }
+}
+
+async function init() {
+  const configRes = await fetch('/config');
+  const { googleClientId } = await configRes.json();
+
+  google.accounts.id.initialize({
+    client_id: googleClientId,
+    callback: handleCredentialResponse,
+  });
+  google.accounts.id.renderButton(loginContainer, { theme: 'outline', size: 'large' });
+
+  const meRes = await fetch('/me');
+  const { user } = await meRes.json();
+  if (user) {
+    showLoggedIn(user);
+  } else {
+    showLoggedOut();
+  }
+}
+
+sendBtn.addEventListener('click', () => {
+  const text = messageInput.value.trim();
+  if (!text) return;
+  socket.emit('send_message', text);
+  messageInput.value = '';
+  statusEl.textContent = 'Отправлено';
+  setTimeout(() => { statusEl.textContent = ''; }, 1500);
+});
+
+messageInput.addEventListener('keydown', (e) => {
+  if (e.key === 'Enter' && (e.ctrlKey || e.metaKey)) {
+    sendBtn.click();
+  }
+});
+
+socket.on('send_error', (msg) => {
+  statusEl.textContent = 'Ошибка: ' + msg;
+});
+
+logoutBtn.addEventListener('click', async () => {
+  await fetch('/auth/logout', { method: 'POST' });
+  showLoggedOut();
+});
+
+init();