fix: federation avatar colors, cross-instance DMs, and instance persistence

- Fix avatar gradient colors in 7 UI sites by using homeUserId fallback
- Merge remote DM channels in populateFromReady (no longer home-only)
- Remove isHome guards from 8 DM WS event handlers for cross-instance DMs
- Route DM typing events to correct instance origin
- Fix autoConnectAll deleting disconnected instances from localStorage
- Distinguish network errors from auth errors in instance reconnection
- Start WebSocket retry for network-unreachable instances (auto-recovery)
- Add reconnectInstance method and Reconnect button in UI

packages/web/src/components/modals/UserSettings.tsx

@@ -65,7 +65,7 @@ export function UserSettingsModal() {
             name={user.displayName ?? user.username}
             size={64}
             status={user.status}
-            userId={user.id}
+            userId={user.homeUserId ?? user.id}
           />
           <div>
             <div className="font-bold text-lg">{user.displayName ?? user.username}</div>