Split view, personal modes, budget warnings, server move script

- Up to three chats side by side (#/s/a+b+c), "Open beside" in the sidebar menu
- File manager tabs of a chat stored per user on the server (/sessions/{id}/tabs)
- Personal modes for every user (Settings → My modes, /account/modes)
- Budget meters (total, provider, images, opencode Go windows) with push warnings
  for admins at the warning share and 100 %, shown in the status overlay
- scripts/move-server.sh: move to another Docker host with bind mounts (Unraid);
  scripts/smoke-test.sh

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/src/cli_api.rs

@@ -23,7 +23,7 @@ use tokio_util::sync::CancellationToken;
 pub async fn config(Extension(user): Extension<User>, State(app): State<AppState>) -> ApiResult {
     let cfg = app.config();
     let root = app.user_roots(Some(&user.id)).into_iter().next().unwrap_or_else(|| app.workspace());
-    let agents: Vec<Value> = crate::prompts::agents(&app, &root, &root)
+    let agents: Vec<Value> = crate::prompts::agents_for(&app, &root, &root, Some(&user.id))
         .into_iter()
         .map(|a| {
             let mut v = json!(a);