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>

web/src/App.tsx

@@ -1,7 +1,7 @@
 import { lazy, Suspense, useEffect, useState } from "react";
 import { connectEvents, get, setUnauthorizedHandler } from "./api";
 import { useT } from "./i18n";
-import { navigate, useRoute } from "./router";
+import { navigate, useRoute, closePane, MAX_PANES } from "./router";
 import { applyEvent, loadSessions, resync, setState } from "./store";
 import type { Info } from "./types";
 import { Sidebar } from "./components/Sidebar";
@@ -80,7 +80,18 @@ export function App() {
 
   const [section, arg] = route;
   let content;
-  if (section === "s" && arg) content = <ChatView key={arg} sessionId={arg} onMenu={() => setMenuOpen(true)} />;
+  const chatIds = section === "s" && arg ? arg.split("+").filter(Boolean).slice(0, MAX_PANES) : [];
+  if (chatIds.length === 1) content = <ChatView key={chatIds[0]} sessionId={chatIds[0]} onMenu={() => setMenuOpen(true)} />;
+  else if (chatIds.length > 1)
+    content = (
+      <div className="split-view">
+        {chatIds.map((id) => (
+          <div key={id} className="split-pane">
+            <ChatView sessionId={id} onMenu={() => setMenuOpen(true)} onClosePane={() => closePane(id)} />
+          </div>
+        ))}
+      </div>
+    );
   else if (section === "settings") content = <Settings tab={arg} onMenu={() => setMenuOpen(true)} />;
   else if (section === "stats") content = <Stats onMenu={() => setMenuOpen(true)} />;
   else if (section === "images") content = <Images onMenu={() => setMenuOpen(true)} />;
@@ -102,7 +113,7 @@ export function App() {
   return (
     <div className="app">
       {menuOpen && <div className="backdrop" onClick={() => setMenuOpen(false)} />}
-      <Sidebar open={menuOpen} activeId={section === "s" ? arg : undefined} section={section ?? ""} />
+      <Sidebar open={menuOpen} activeIds={chatIds} section={section ?? ""} />
       <main className="main">{content}</main>
       <WhatsNew version={info.version} />
       <Palette />