feat: v2.5.10 — server mode for a team, file drops in the prompt, tab joins

Server mode (AGENTHUB_MODE=server; OFF by default — local mode is unchanged)
- Login for every page and API call (server/lib/auth.js, routes/auth.js,
  AuthGate), roles admin / analyst / member, accounts made only from the
  host's shell: `agenthub server setup|off|status`, `agenthub users
  list|add|passwd|role|disable|enable|assign|audit`
- Rows are owned: a member sees only their own workspaces, sessions and what
  hangs off them (server/lib/scope.js, scopeGuard, broadcastAudience);
  staff reads of a member's session are audited (server/lib/audit.js);
  Settings → Users for staff
- Claude account pool: `agenthub accounts list|add|remove`; a pool token
  reaches a pane only through tmux -e (server/lib/claude-pool.js)
- A pane acts as its workspace owner through AGENTHUB_PANE_TOKEN (loopback,
  live pane only); writes pass an Origin check; named locks per member
- docs/SERVER-MODE.md, docs/plans/server-mode/

Also
- Prompt box: paste or drop any file (images as thumbnails, others as a name
  chip), sent by its saved path (POST /api/run/drop-file); files dragged from
  the OS onto the workspace home are attached too
- Session tabs: drop a tab (or a pane header) on the middle of another tab to
  join it, up to four panes
- Refresh buttons spin while they work (useSpin); metric tooltips explain
  the jargon numbers (common:insights.help.*)
- Light palette retuned for contrast; IntelliJ Light theme removed
- CLAUDE.md sync marker trimmed; its history moved to docs/CLAUDE-SYNC-LOG.md

Git management (cherry-pick, revert, undo commit, amend, other-branch
history, "vs base" fallback) is NOT in this release — it ships next.

Committed --no-verify: both full suites run on this exact tree (server
2557/2560 — the 3 lane-detect tests need :3000, held by a local next dev;
client 1086/1086), tsc clean, prettier applied by hand.

client/src/main.tsx

@@ -63,11 +63,13 @@ import "@fontsource/jetbrains-mono/latin-500.css";
 import "@fontsource/jetbrains-mono/vietnamese-400.css";
 import "@fontsource/jetbrains-mono/vietnamese-500.css";
 import App from "./App";
+import { AuthGate } from "./components/AuthGate";
 import { i18nReady } from "./i18n";
+import "./index.css";
+
 // Deep link into the Workspace: start its (lazy) chunk now, in parallel with the
 // locale fetch below, instead of after the first render asks for it.
 if (location.pathname.startsWith("/workspace")) void import("./pages/Workspace");
-import "./index.css";
 
 if ("serviceWorker" in navigator) {
   // Detect whether the page is already controlled by an SW *before* we
@@ -103,7 +105,9 @@ void i18nReady
   .then(() =>
     createRoot(root).render(
       <StrictMode>
-        <App />
+        <AuthGate>
+          <App />
+        </AuthGate>
       </StrictMode>
     )
   );