fix(security): stream tickets instead of session tokens in URLs (FLAW-22)

WebSocket and EventSource put the 30-day session token into the URL,
where proxies log it. The app now gets a one-time ticket right before
connecting (POST /auth/stream-ticket, 60 s, bound to the token version);
?token= is no longer accepted for streams, non-browser clients may use
the Authorization header.

With BASE_URL set, CORS allows only that origin and WebSocket upgrades
only it or the requested host; credentials are off (no cookies exist).
Logout, ending all sessions, a new password and deactivation close all
live streams of the account; clients with a valid session reconnect
with a fresh ticket.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/lib/api.ts

@@ -1209,19 +1209,28 @@ let isRealtimeConnectedState = false;
 let manualDisconnect = false;
 let wsReconnectDelay = 2000;
 
-export function buildWebSocketURL(listId?: string): string {
-  const protocol = window.location.protocol === 'https:' ? 'wss:' : 'ws:';
-  const token = getToken() || '';
-  if (listId) {
-    return `${protocol}//${window.location.host}/api/v1/ws/lists/${encodeURIComponent(listId)}?token=${encodeURIComponent(token)}`;
+// WebSocket and EventSource cannot send headers, so instead of the session token (which would land in
+// proxy logs) every connection gets a one-time ticket, valid for a minute (POST /auth/stream-ticket).
+async function fetchStreamTicket(): Promise<string | null> {
+  try {
+    const res = await request<{ ticket?: string }>('/api/v1/auth/stream-ticket', { method: 'POST' });
+    return res?.ticket || null;
+  } catch {
+    return null;
   }
-  return `${protocol}//${window.location.host}/api/v1/ws?token=${encodeURIComponent(token)}`;
 }
 
-export function buildSSEURL(listId?: string, docId?: string, rooms?: string[]): string {
-  const token = getToken() || '';
+export function buildWebSocketURL(ticket: string, listId?: string): string {
+  const protocol = window.location.protocol === 'https:' ? 'wss:' : 'ws:';
+  if (listId) {
+    return `${protocol}//${window.location.host}/api/v1/ws/lists/${encodeURIComponent(listId)}?ticket=${encodeURIComponent(ticket)}`;
+  }
+  return `${protocol}//${window.location.host}/api/v1/ws?ticket=${encodeURIComponent(ticket)}`;
+}
+
+export function buildSSEURL(ticket: string, listId?: string, docId?: string, rooms?: string[]): string {
   const params = new URLSearchParams();
-  if (token) params.set('token', token);
+  params.set('ticket', ticket);
   if (listId) params.set('listId', listId);
   if (docId) params.set('docId', docId);
   if (rooms && rooms.length > 0) params.set('rooms', rooms.join(','));
@@ -1309,7 +1318,9 @@ function switchToSSE(reason: string) {
   connectSSE();
 }
 
-export function connectSSE(rooms?: string[]): void {
+let sseTicketPending = false;
+
+export async function connectSSE(rooms?: string[]): Promise<void> {
   if (rooms) {
     rooms.forEach((r) => globalSubscribedRooms.add(r));
   }
@@ -1328,8 +1339,20 @@ export function connectSSE(rooms?: string[]): void {
     activeGlobalSSE = null;
   }
 
+  if (sseTicketPending) return;
+  sseTicketPending = true;
+  const ticket = await fetchStreamTicket();
+  sseTicketPending = false;
+  if (manualDisconnect || !getToken()) return;
+  if (!ticket) {
+    // Server unreachable or session gone: try again later like after a dropped stream
+    notifyRealtimeStatusChange(false, 'none');
+    sseReconnectTimer = setTimeout(() => connectSSE(), sseReconnectDelay);
+    return;
+  }
+
   try {
-    const url = buildSSEURL(undefined, undefined, Array.from(globalSubscribedRooms));
+    const url = buildSSEURL(ticket, undefined, undefined, Array.from(globalSubscribedRooms));
     const es = new EventSource(url);
     activeGlobalSSE = es;
 
@@ -1402,15 +1425,16 @@ export function connectSSE(rooms?: string[]): void {
   }
 }
 
-export function connectWebSocket(): void {
+let wsTicketPending = false;
+
+export async function connectWebSocket(): Promise<void> {
   const token = getToken();
   if (!token) return;
   manualDisconnect = false;
 
   // If proxy blocked WebSocket previously, do not attempt failing WebSocket; stay on SSE
   if (isWsBlockedByProxy) {
-    connectSSE();
-    return;
+    return connectSSE();
   }
 
   if (activeGlobalWS && (activeGlobalWS.readyState === WebSocket.OPEN || activeGlobalWS.readyState === WebSocket.CONNECTING)) {
@@ -1421,8 +1445,22 @@ export function connectWebSocket(): void {
   clearTimeout(wsReconnectTimer);
   clearTimeout(sseReconnectTimer);
 
+  if (wsTicketPending) return;
+  wsTicketPending = true;
+  const ticket = await fetchStreamTicket();
+  wsTicketPending = false;
+  if (manualDisconnect || !getToken()) return;
+  if (activeGlobalWS && (activeGlobalWS.readyState === WebSocket.OPEN || activeGlobalWS.readyState === WebSocket.CONNECTING)) {
+    return;
+  }
+  if (!ticket) {
+    notifyRealtimeStatusChange(false, 'none');
+    wsReconnectTimer = setTimeout(() => connectWebSocket(), wsReconnectDelay);
+    return;
+  }
+
   try {
-    const url = buildWebSocketURL();
+    const url = buildWebSocketURL(ticket);
     const ws = new WebSocket(url);
     activeGlobalWS = ws;