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>

Doku/reverse-proxy.md

@@ -236,7 +236,8 @@ curl -i -N \
   -H "Origin: https://mindsift.example.com" \
   -H "Sec-WebSocket-Key: SGVsbG8sIHdvcmxkIQ==" \
   -H "Sec-WebSocket-Version: 13" \
-  https://mindsift.example.com/api/v1/ws?token=<DEIN_TOKEN>
+  -H "Authorization: Bearer <DEIN_TOKEN>" \
+  https://mindsift.example.com/api/v1/ws
 ```
 *Erwartete Antwort:* `101 Switching Protocols`