feat: 统一调试模块 debug.ts，VITE_DEBUG 环境变量控制调试面板显隐

- 新增 services/debug.ts: isDebug()/debugLog()/getDebugLogs()
- .env 中 VITE_DEBUG=true 开启调试，false 关闭
- LoginPage 使用 debugLog() 记录登录流程
- ProfilePage 通过 isDebug() 控制调试面板显隐
- .env.example 同步更新

frontend/src/app/pages/LoginPage.tsx

@@ -3,7 +3,8 @@ import { useNavigate } from "react-router";
 import { motion } from "motion/react";
 import { Heart } from "lucide-react";
 import { useUser } from "../context/UserContext";
-import { devLogin, createDummyToken, getToken } from "../services/api";
+import { devLogin, createDummyToken } from "../services/api";
+import { debugLog, clearDebugLogs } from "../services/debug";
 
 export function LoginPage() {
   const navigate = useNavigate();
@@ -11,34 +12,49 @@ export function LoginPage() {
   const [error, setError] = useState("");
 
   useEffect(() => {
-    const params = new URLSearchParams(window.location.search);
+    clearDebugLogs();
+
+    const params = new URLSearchParams(window.location.search);
+    debugLog(`URL: ${window.location.href.substring(0, 100)}`);
+    debugLog(`search: ${window.location.search}`);
 
-    // URL 参数 uid/openid/phone 直接构建本地 token 登录
     const openidParam = params.get('openid');
-    if (openidParam) {
+    if (openidParam && openidParam.trim()) {
       const uid = parseInt(params.get('uid') || '0');
       const phone = params.get('phone') || '';
       const token = createDummyToken(uid, openidParam, phone);
+      debugLog(`dummy token: ${token.substring(0, 50)}...`);
+
+      try {
+        const payload = JSON.parse(atob(token.split('.')[1]));
+        debugLog(`payload: uid=${payload.uid}, openid=${payload.openid}, phone=${payload.phone}`);
+      } catch (e: any) {
+        debugLog(`decode error: ${e.message}`);
+      }
+
       setTokenAndUser(token, { id: String(uid), openid: openidParam, phone });
+      debugLog(`setTokenAndUser: id=${uid}, openid=${openidParam}, phone=${phone}`);
+
       fetchProfile().then((dto) => {
+        if (dto) debugLog(`fetchProfile: name=${dto.name}, phone=${dto.phone}, onboarded=${dto.is_onboarded}`);
         navigate(dto?.is_onboarded ? "/home" : "/onboarding", { replace: true });
-      }).catch(() => {
+      }).catch((e: any) => {
+        debugLog(`fetchProfile error: ${e?.message}`);
         setError("登录已失效，请在小程序重新进入");
       });
       return;
     }
 
-    // 浏览器开发环境 → dev-login
+    debugLog(`no openid param (val=${openidParam || '(empty)'}), fallback to dev-login`);
     devLogin().then((res) => {
-      setTokenAndUser(res.token, {
-        id: res.user_id,
-        openid: res.openid,
-        phone: res.mobile,
-      });
+      debugLog(`dev-login: openid=${res.openid}, phone=${res.mobile}`);
+      setTokenAndUser(res.token, { id: res.user_id, openid: res.openid, phone: res.mobile });
       fetchProfile().then((dto) => {
+        if (dto) debugLog(`fetchProfile: name=${dto.name}, phone=${dto.phone}`);
         navigate(dto?.is_onboarded ? "/home" : "/onboarding", { replace: true });
       });
     }).catch((err) => {
+      debugLog(`dev-login error: ${err?.message}`);
       setError(err?.message || "登录失败，请刷新重试");
     });
   }, []); // eslint-disable-line react-hooks/exhaustive-deps

frontend/src/app/pages/ProfilePage.tsx

@@ -24,6 +24,7 @@ import { Button } from "../components/ui/button";
 import { Card } from "../components/ui/card";
 import { Badge } from "../components/ui/badge";
 import { useUser, getPregnancyStage } from "../context/UserContext";
+import { isDebug, getDebugLogs } from "../services/debug";
 
 interface UserInfo {
   name: string;
@@ -187,8 +188,23 @@ export function ProfilePage() {
     </div>
   );
 
+  // 🐞 调试面板（VITE_DEBUG=true 时显示）
+  const [debugLog] = useState<string[]>(() => isDebug() ? getDebugLogs() : []);
+  const [showDebug, setShowDebug] = useState(false);
+
   return (
-    <div className="min-h-dvh bg-morandi-50">
+    <div className="min-h-dvh bg-morandi-50 pb-20">
+      {/* 🐞 调试面板 */}
+      {debugLog.length > 0 && (
+        <div className="bg-black/80 text-white text-xs font-mono p-3">
+          <button onClick={() => setShowDebug(!showDebug)} className="text-yellow-400 font-bold mb-1">
+            🐞 {showDebug ? '收起' : '展开'}调试日志 ({debugLog.length}条)
+          </button>
+          {showDebug && debugLog.map((line, i) => (
+            <div key={i} className="text-green-300 break-all">{line}</div>
+          ))}
+        </div>
+      )}
       {/* 顶部导航 */}
       <div className="bg-white border-b border-gray-100 sticky top-0 z-10">
         <div className="mx-auto px-4 py-4 flex items-center justify-between">