fix(settings): resync push-rule toggle from account-data; MSC1929 support host

- PushRuleEditor: the enable Switch initialized its state from pushRule.enabled
  once (useState initializer), so a rule toggled on another device left the
  Switch stale until remount. A useEffect now resyncs on pushRule.enabled
  change. pushRule flows from useAccountData(m.push_rules), which re-renders on
  sync, so the resync is genuinely reached; no optimistic-update conflict (the
  toggle sets state only after the PUT resolves).

- About: the "Homeserver Support" panel fetched /.well-known/matrix/support from
  the client-API URL (mx.getHomeserverUrl()). Per MSC1929 that file lives at the
  MXID server-name host (like /.well-known/matrix/client), which differs on
  delegated/split-domain servers. Now fetched from https://{mx.getDomain()};
  identical target for non-delegated servers (incl. Lotus), spec-correct for
  delegated ones, and degrades gracefully (catch → panel hidden) otherwise.

Bug-hunt findings from LOTUS_TODO. Two review agents; both confirmed effective
and non-regressing (full account-data re-render chain traced; CORS/host edge
weighed). Gate-green (tsc, eslint, prettier, 914 tests, build).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/features/settings/about/About.tsx

@@ -42,9 +42,16 @@ function useServerSupport(): { support: MSC1929Support | null; loading: boolean
 
   useEffect(() => {
     const controller = new AbortController();
-    const baseUrl = mx.getHomeserverUrl();
+    // MSC1929 support info is served from the MXID server-name host (like
+    // /.well-known/matrix/client), which on delegated/split-domain servers is
+    // NOT the client-API URL. Derive it from the user's domain.
+    const serverName = mx.getDomain();
+    if (!serverName) {
+      setLoading(false);
+      return undefined;
+    }
     setLoading(true);
-    fetch(`${baseUrl}/.well-known/matrix/support`, { signal: controller.signal })
+    fetch(`https://${serverName}/.well-known/matrix/support`, { signal: controller.signal })
       .then((res) => {
         if (!res.ok) return null;
         return res.json();