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/plugins/react-custom-html-parser.tsx

@@ -122,11 +122,15 @@ const cleanHref = (href: string): string =>
   stripTrackingOnRender ? stripTrackingParams(href) : href;
 
 // [Gitea #130] Links to THIS deployment's room routes render and click like
-// matrix.to links. The base is set once from the client config
-// (ClientNonUIFeatures) because this module has no access to hooks.
-let lotusPermalinkBase: string | undefined;
-export const setLotusPermalinkBase = (baseUrl: string | undefined): void => {
-  lotusPermalinkBase = baseUrl;
+// matrix.to links. The bases are set once from the client config
+// (ClientNonUIFeatures) because this module has no access to hooks. [Gitea
+// #248] Several: the desktop app knows both its local origin and the public web
+// app (`webAppUrl`), and people share the public one.
+let lotusPermalinkBases: string[] = [];
+export const setLotusPermalinkBase = (baseUrls: string | string[] | undefined): void => {
+  lotusPermalinkBases = (Array.isArray(baseUrls) ? baseUrls : [baseUrls]).filter(
+    (b): b is string => !!b,
+  );
 };
 /**
  * The matrix.to form of `href` when it is a matrix.to link or a Lotus
@@ -134,7 +138,11 @@ export const setLotusPermalinkBase = (baseUrl: string | undefined): void => {
  */
 export const toMatrixToHref = (href: string): string | undefined => {
   if (testMatrixTo(href)) return href;
-  return lotusPermalinkBase ? lotusPermalinkToMatrixTo(lotusPermalinkBase, href) : undefined;
+  for (const base of lotusPermalinkBases) {
+    const matrixTo = lotusPermalinkToMatrixTo(base, href);
+    if (matrixTo) return matrixTo;
+  }
+  return undefined;
 };
 
 export const LINKIFY_OPTS: LinkifyOpts = {