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/pages/Settings.tsx

@@ -120,6 +120,7 @@ import type { WSMessage } from "../lib/types";
 import { confirmDialog } from "../lib/confirm";
 import { toast } from "../lib/toast";
 import { useDialog } from "../hooks/useDialog";
+import { useSpin } from "../hooks/useSpin";
 import { exportPrefs, importPrefs } from "../lib/prefsBackup";
 
 /** The fewest milliseconds between two activity-driven `/settings/info` reads:
@@ -249,6 +250,7 @@ export function Settings({
       setLoading(false);
     }
   }, [t, needsInfo, section]);
+  const [spinning, refresh] = useSpin(load);
 
   useEffect(() => {
     load();
@@ -814,8 +816,14 @@ export function Settings({
                   <FileDown className="w-3.5 h-3.5" />
                   {t("exportData")}
                 </a>
-                <button onClick={load} className="btn-ghost">
-                  <RefreshCw className="w-4 h-4" /> {t("common:refresh")}
+                <button
+                  onClick={refresh}
+                  disabled={spinning}
+                  aria-busy={spinning}
+                  className="btn-ghost"
+                >
+                  <RefreshCw className={`w-4 h-4 ${spinning ? "animate-spin" : ""}`} />{" "}
+                  {t("common:refresh")}
                 </button>
               </div>
             </div>