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/components/AlertsNotifications.tsx

@@ -92,6 +92,7 @@ import { ContextMenu, MenuItem, MenuSeparator, useContextMenu } from "./ContextM
 import { fmtCost, timeAgo } from "../lib/format";
 import { toast } from "../lib/toast";
 import { useAiTools } from "../hooks/useAiTools";
+import { useSpin } from "../hooks/useSpin";
 import type { AlertEvent, AlertRule, AlertRuleType, RulePreview, WSMessage } from "../lib/types";
 
 const PAGE_SIZE = 25;
@@ -342,6 +343,7 @@ export function AlertsNotifications() {
       setLoadingAlerts(false);
     }
   }, [unackedOnly, t]);
+  const [spinning, refreshAlerts] = useSpin(loadAlerts);
 
   const loadMore = useCallback(async () => {
     try {
@@ -1017,11 +1019,13 @@ export function AlertsNotifications() {
                 label={t("feed.unackedOnly")}
               />
               <button
-                onClick={() => loadAlerts()}
+                onClick={refreshAlerts}
+                disabled={spinning}
+                aria-busy={spinning}
                 className="btn-ghost border border-border inline-flex items-center gap-1.5 text-xs"
                 title={t("refresh")}
               >
-                <RefreshCw className="w-3.5 h-3.5" />
+                <RefreshCw className={`w-3.5 h-3.5 ${spinning ? "animate-spin" : ""}`} />
               </button>
               {unacked > 0 && (
                 <button