feat: paper page show latest signal per coin

frontend/app/paper/page.tsx

@@ -108,6 +108,61 @@ function SummaryCards() {
   );
 }
 
+// ─── 最新信号状态 ────────────────────────────────────────────────
+
+const COINS = ["BTCUSDT", "ETHUSDT", "XRPUSDT", "SOLUSDT"];
+
+function LatestSignals() {
+  const [signals, setSignals] = useState<Record<string, any>>({});
+  useEffect(() => {
+    const f = async () => {
+      for (const sym of COINS) {
+        try {
+          const r = await authFetch(`/api/signals/latest?symbol=${sym}`);
+          if (r.ok) {
+            const j = await r.json();
+            setSignals(prev => ({ ...prev, [sym]: j }));
+          }
+        } catch {}
+      }
+    };
+    f(); const iv = setInterval(f, 15000); return () => clearInterval(iv);
+  }, []);
+
+  return (
+    <div className="rounded-xl border border-slate-200 bg-white overflow-hidden">
+      <div className="px-3 py-2 border-b border-slate-100">
+        <h3 className="font-semibold text-slate-800 text-xs">最新信号</h3>
+      </div>
+      <div className="divide-y divide-slate-50">
+        {COINS.map(sym => {
+          const s = signals[sym];
+          const coin = sym.replace("USDT", "");
+          const ago = s?.ts ? Math.round((Date.now() - s.ts) / 60000) : null;
+          return (
+            <div key={sym} className="px-3 py-1.5 flex items-center justify-between">
+              <div className="flex items-center gap-2">
+                <span className="font-mono text-xs font-bold text-slate-700 w-8">{coin}</span>
+                {s?.signal ? (
+                  <>
+                    <span className={`text-xs font-bold ${s.signal === "LONG" ? "text-emerald-600" : "text-red-500"}`}>
+                      {s.signal === "LONG" ? "🟢" : "🔴"} {s.signal}
+                    </span>
+                    <span className="font-mono text-[10px] text-slate-500">{s.score}分</span>
+                  </>
+                ) : (
+                  <span className="text-[10px] text-slate-400">⚪ 无信号</span>
+                )}
+              </div>
+              {ago !== null && <span className="text-[10px] text-slate-400">{ago < 60 ? `${ago}m前` : `${Math.round(ago/60)}h前`}</span>}
+            </div>
+          );
+        })}
+      </div>
+    </div>
+  );
+}
+
 // ─── 当前持仓 ────────────────────────────────────────────────────
 
 function ActivePositions() {
@@ -378,6 +433,7 @@ export default function PaperTradingPage() {
 
       <ControlPanel />
       <SummaryCards />
+      <LatestSignals />
       <ActivePositions />
       <EquityCurve />
       <TradeHistory />