fix(desktop): Lotus links use the public web app, and open in-app (#248)

Lotus permalinks (#130) were built from window.location.origin. In the
desktop app that's the local tauri-plugin-localhost server (hash-routed), so
"Copy Lotus Link" copied e.g. http://localhost:…/#/home/!room…, which works
for nobody else. And the link recogniser only knew that local base, so a real
https://chat.lotusguild.org/home/… link in a message opened the browser
instead of the room.

- useLotusShareBase: in the desktop app, links for other people use config
  `webAppUrl` (https only, set by cinny-desktop #23) in web path-routing
  form; otherwise the origin, as before. Used by "Copy Lotus Link" on
  messages, the space menu and space tabs.
- The recogniser accepts several bases: the origin, plus `webAppUrl` in the
  desktop app.
- The web app is unchanged.

Verified with a simulated desktop (Tauri bridge + webAppUrl) against a local
Synapse. Copied links are https://chat.lotusguild.org/home/<room>/<event> and
https://chat.lotusguild.org/<space>. A public link in a message renders as
the room pill and clicking it opens the room in-app, with nothing sent to the
system browser. The web app still copies origin links. Unit tests for the
base selection; Playwright 20 passed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/app/pages/client/ClientNonUIFeatures.tsx

@@ -77,6 +77,7 @@ import { KeyboardShortcutsDialog, useKeyboardShortcutsTrigger } from '../../feat
 import { useRoomsListener } from '../../hooks/useRoomsListener';
 import { threadNotificationsAtom } from '../../state/threadNotifications';
 import { roomIdToActiveThreadIdAtomFamily } from '../../state/room/thread';
+import { lotusLinkBases } from '../../hooks/useLotusLinkBase';
 import {
   getThreadNotificationMode,
   shouldNotifyThreadReply,
@@ -118,11 +119,12 @@ function SystemEmojiFeature() {
 
 // [Gitea #103] Mirror the privacy toggle into the html parser's module flag.
 function LotusPermalinkFeature() {
-  const { hashRouter } = useClientConfig();
+  const { hashRouter, webAppUrl } = useClientConfig();
   useEffect(() => {
-    setLotusPermalinkBase(getOriginBaseUrl(hashRouter));
+    // [Gitea #248] In the desktop app, links to the public web app count too.
+    setLotusPermalinkBase(lotusLinkBases(getOriginBaseUrl(hashRouter), isTauriApp(), webAppUrl));
     return () => setLotusPermalinkBase(undefined);
-  }, [hashRouter]);
+  }, [hashRouter, webAppUrl]);
   return null;
 }