fix(notifications): notification replies re-check encryption at send time and use the right account (#299)

The service worker posts inline notification replies in the clear (it
cannot encrypt). The Reply action was only withheld for rooms that were
encrypted when the notification was shown, so a reply typed hours later
into a room that has since turned on encryption went out unencrypted.
It also posted with the newest session the worker knew, not the
notification's account.

The worker now GETs the room's m.room.encryption state first and only
sends on a definite 404; notifications carry the user id and the worker
uses that account's session (or refuses). "Reply not sent" says why.

Fixes #299

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

src/sw-session.ts

@@ -1,4 +1,4 @@
-export function pushSessionToSW(baseUrl?: string, accessToken?: string) {
+export function pushSessionToSW(baseUrl?: string, accessToken?: string, userId?: string) {
   if (!('serviceWorker' in navigator)) return;
   if (!navigator.serviceWorker.controller) return;
 
@@ -6,5 +6,6 @@ export function pushSessionToSW(baseUrl?: string, accessToken?: string) {
     type: 'setSession',
     accessToken,
     baseUrl,
+    userId,
   });
 }