refactor(desktop): AuthContext exposes userKeyState instead of device record

Replaces the per-device DeviceRecord lookup with a per-user discriminated
union (loading | needs-setup | needs-unlock | unlocked). Heartbeat block
deleted (telemetry no longer device-bound); webPush keyed by install-id.

apps/desktop/src/components/ForwardDialog.tsx

@@ -14,6 +14,7 @@ import { useTranslation } from 'react-i18next';
 
 import { useAuth } from '../context/AuthContext';
 import { useConversationsContext } from '../context/ConversationsContext';
+import { ensureInstallId } from '../lib/installId';
 import { supabase } from '../lib/supabase';
 import { cachedUserKey } from '../lib/userIdentity';
 import { Avatar } from './Avatar';
@@ -32,7 +33,7 @@ interface Props {
 // preview hints at the dropped attachment.
 export function ForwardDialog({ open, message, currentConversationId, onClose }: Props) {
   const { t } = useTranslation(['app', 'errors']);
-  const { session, device } = useAuth();
+  const { session } = useAuth();
   const { conversations } = useConversationsContext();
 
   const [selected, setSelected] = useState<Set<string>>(new Set());
@@ -83,7 +84,7 @@ export function ForwardDialog({ open, message, currentConversationId, onClose }:
   }
 
   async function handleSend() {
-    if (!session?.user.id || !device?.id || !message) return;
+    if (!session?.user.id || !message) return;
     if (selected.size === 0) return;
     setBusy(true);
     setError(null);
@@ -137,7 +138,7 @@ export function ForwardDialog({ open, message, currentConversationId, onClose }:
           conversationId: convId,
           plaintext: text,
           senderUserId: session.user.id,
-          senderDeviceId: device.id,
+          senderDeviceId: ensureInstallId(),
           senderPrivateKey: priv,
           ...(newHandles.length > 0 ? { attachmentHandles: newHandles } : {}),
         });