feat(share): send from inside the share sheet — the Teams-style in-extension picker

Replaces the wrong approach (stage + try to bounce into the app, which iOS blocks)
with the one Teams/WhatsApp actually use: the picker and the send happen INSIDE the
share extension, so there's no app-open at all. Tap Share → Biz Connect → pick a
chat → it uploads and sends, right there in the sheet.

How the extension can send without the app: it's a separate process that can't see
the web app's HttpOnly cookie, so:
- server: GET /api/share/token mints a bearer token for the logged-in user.
- web: on every launch the app fetches that token and hands it to the extension via
  the App Group (ShareInbox.setAuth writes token+base to the shared UserDefaults).
- extension: reads the token and calls the SAME API the native client uses —
  GET /api/messages/conversations to list chats, POST /api/messages/upload for each
  file, POST /api/messages to send. Native UITableView picker with search.

Robustness: it still stages the files + writes a manifest first, so if there's no
token yet (user never signed in) or the send fails, the file isn't lost — the app
collects it on next open, exactly as before. On success the manifest is cleared so
the app doesn't re-offer it.

Server + web are live now; the token endpoint is harmless until a build ships the
extension. NEEDS A NEW iOS BUILD for the picker itself.

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

server/public/home.html

@@ -3528,6 +3528,17 @@ async function sendMessage(){
 // build) or there's nothing pending, this is a no-op.
 let _shareBusy=false;
 function bzShareInbox(){ const P=window.Capacitor&&window.Capacitor.Plugins; return P&&P.ShareInbox||null; }
+// Hand the Share Extension a bearer token + API base so it can list chats, upload and send on its own —
+// the Teams-style in-sheet picker, no app-open needed. The extension can't read our HttpOnly cookie, so
+// the logged-in web app mints a token (/api/share/token) and writes it into the App Group each launch.
+async function bzPushShareAuth(){
+  const SI=bzShareInbox(); if(!SI||!SI.setAuth||!ME||!ME.id) return;
+  try{
+    const r=await fetch('/api/share/token'); if(!r.ok) return;
+    const d=await r.json(); if(!d||!d.token) return;
+    await SI.setAuth({ token:d.token, base:location.origin });
+  }catch(_){}
+}
 async function bzCheckSharedInbox(){
   const SI=bzShareInbox(); if(!SI||_shareBusy) return;
   if(!ME||!ME.id) return;                                  // must be signed in to choose a conversation
@@ -5663,6 +5674,8 @@ window.addEventListener('message',(e)=>{
   // Cold launch FROM the share sheet: the extension staged files before the app was even running, so
   // the appUrlOpen listener may have missed it. Sweep once now that ME + the chat list are ready.
   setTimeout(bzCheckSharedInbox, 600);
+  // Refresh the token the Share Extension uses to send on its own (Teams-style in-sheet picker).
+  bzPushShareAuth();
 })();
 
 // GUEST meeting: a lightweight pre-join (name) then join the call with a throwaway guest identity —