feat: 完成多用户系统（登录/注册界面 + 用户隔离）

frontend-react/src/App.js

@@ -4,6 +4,8 @@ import StatsPanel from './components/StatsPanel';
 import Calendar from './components/Calendar';
 import DiaryDetail from './components/DiaryDetail';
 import ExperienceList from './components/ExperienceList';
+import Login from './components/Login';
+import Register from './components/Register';
 
 const API_BASE = '/api';
 
@@ -11,6 +13,7 @@ const API_BASE = '/api';
  * ⚠️ 主应用组件
  * 
  * 核心功能：
+ * - 用户认证
  * - 统计面板
  * - 日历组件 ⭐
  * - 日记详情
@@ -19,6 +22,8 @@ const API_BASE = '/api';
  * ⚠️ 修改前阅读 docs/README.md
  */
 function App() {
+  const [user, setUser] = useState(null);
+  const [authView, setAuthView] = useState('login'); // login | register
   const [selectedDate, setSelectedDate] = useState(new Date().toISOString().split('T')[0]);
   const [diaryDates, setDiaryDates] = useState([]);
   const [entries, setEntries] = useState([]);
@@ -28,9 +33,50 @@ function App() {
   const [error, setError] = useState(null);
 
   useEffect(() => {
-    loadData();
+    // 检查是否已登录
+    checkAuth();
   }, []);
 
+  const checkAuth = async () => {
+    try {
+      const res = await axios.get(`${API_BASE}/auth/me/`);
+      setUser(res.data);
+      loadData();
+    } catch (err) {
+      setLoading(false);
+    }
+  };
+
+  const handleLogin = (userData, view) => {
+    if (view) {
+      setAuthView(view);
+    } else if (userData) {
+      setUser(userData);
+      loadData();
+    }
+  };
+
+  const handleRegister = (userData, view) => {
+    if (view) {
+      setAuthView(view);
+    } else if (userData) {
+      setUser(userData);
+      loadData();
+    }
+  };
+
+  const handleLogout = async () => {
+    try {
+      await axios.post(`${API_BASE}/auth/logout/`);
+      setUser(null);
+      setEntries([]);
+      setExperiences([]);
+      setStats({});
+    } catch (err) {
+      console.error('登出失败:', err);
+    }
+  };
+
   const loadData = async () => {
     try {
       const [statsRes, entriesRes, expRes] = await Promise.all([
@@ -50,6 +96,14 @@ function App() {
     }
   };
 
+  // 未登录显示登录/注册界面
+  if (!user) {
+    if (authView === 'register') {
+      return <Register onRegister={handleRegister} />;
+    }
+    return <Login onLogin={handleLogin} />;
+  }
+
   const handleDateSelect = (date) => {
     setSelectedDate(date);
   };
@@ -67,8 +121,16 @@ function App() {
   return (
     <div className="container">
       <header>
-        <h1>⚡ 码神的日记系统</h1>
-        <p>记录每天的进步与成长</p>
+        <div className="header-content">
+          <div>
+            <h1>⚡ 码神的日记系统</h1>
+            <p>记录每天的进步与成长</p>
+          </div>
+          <div className="user-info">
+            <span>👤 {user.username}</span>
+            <button onClick={handleLogout} className="btn-logout">登出</button>
+          </div>
+        </div>
       </header>
 
       <StatsPanel stats={stats} />

frontend-react/src/components/Login.js

@@ -0,0 +1,77 @@
+import React, { useState } from 'react';
+import axios from 'axios';
+
+const API_BASE = '/api';
+
+/**
+ * 登录组件
+ */
+function Login({ onLogin }) {
+  const [username, setUsername] = useState('');
+  const [password, setPassword] = useState('');
+  const [error, setError] = useState('');
+  const [loading, setLoading] = useState(false);
+
+  const handleSubmit = async (e) => {
+    e.preventDefault();
+    setLoading(true);
+    setError('');
+
+    try {
+      const res = await axios.post(`${API_BASE}/auth/login/`, {
+        username,
+        password
+      });
+      onLogin(res.data.user);
+    } catch (err) {
+      setError(err.response?.data?.message || '登录失败');
+    } finally {
+      setLoading(false);
+    }
+  };
+
+  return (
+    <div className="auth-container">
+      <div className="auth-card">
+        <h1>⚡ 码神日记系统</h1>
+        <h2>登录</h2>
+        
+        {error && <div className="error">{error}</div>}
+        
+        <form onSubmit={handleSubmit}>
+          <div className="form-group">
+            <label>用户名</label>
+            <input
+              type="text"
+              value={username}
+              onChange={(e) => setUsername(e.target.value)}
+              required
+              placeholder="请输入用户名"
+            />
+          </div>
+          
+          <div className="form-group">
+            <label>密码</label>
+            <input
+              type="password"
+              value={password}
+              onChange={(e) => setPassword(e.target.value)}
+              required
+              placeholder="请输入密码"
+            />
+          </div>
+          
+          <button type="submit" className="btn-primary" disabled={loading}>
+            {loading ? '登录中...' : '登录'}
+          </button>
+        </form>
+        
+        <p className="auth-tip">
+          还没有账号？<a href="#register" onClick={(e) => { e.preventDefault(); onLogin(null, 'register'); }}>立即注册</a>
+        </p>
+      </div>
+    </div>
+  );
+}
+
+export default Login;

frontend-react/src/components/Register.js

@@ -0,0 +1,112 @@
+import React, { useState } from 'react';
+import axios from 'axios';
+
+const API_BASE = '/api';
+
+/**
+ * 注册组件
+ */
+function Register({ onRegister }) {
+  const [username, setUsername] = useState('');
+  const [email, setEmail] = useState('');
+  const [password, setPassword] = useState('');
+  const [confirmPassword, setConfirmPassword] = useState('');
+  const [error, setError] = useState('');
+  const [loading, setLoading] = useState(false);
+
+  const handleSubmit = async (e) => {
+    e.preventDefault();
+    
+    if (password !== confirmPassword) {
+      setError('两次输入的密码不一致');
+      return;
+    }
+    
+    if (password.length < 6) {
+      setError('密码至少 6 位');
+      return;
+    }
+    
+    setLoading(true);
+    setError('');
+
+    try {
+      const res = await axios.post(`${API_BASE}/auth/register/`, {
+        username,
+        email,
+        password
+      });
+      onRegister(res.data.user);
+    } catch (err) {
+      setError(err.response?.data?.username?.[0] || err.response?.data?.message || '注册失败');
+    } finally {
+      setLoading(false);
+    }
+  };
+
+  return (
+    <div className="auth-container">
+      <div className="auth-card">
+        <h1>⚡ 码神日记系统</h1>
+        <h2>注册</h2>
+        
+        {error && <div className="error">{error}</div>}
+        
+        <form onSubmit={handleSubmit}>
+          <div className="form-group">
+            <label>用户名</label>
+            <input
+              type="text"
+              value={username}
+              onChange={(e) => setUsername(e.target.value)}
+              required
+              placeholder="请输入用户名"
+            />
+          </div>
+          
+          <div className="form-group">
+            <label>邮箱（可选）</label>
+            <input
+              type="email"
+              value={email}
+              onChange={(e) => setEmail(e.target.value)}
+              placeholder="请输入邮箱"
+            />
+          </div>
+          
+          <div className="form-group">
+            <label>密码</label>
+            <input
+              type="password"
+              value={password}
+              onChange={(e) => setPassword(e.target.value)}
+              required
+              placeholder="至少 6 位"
+            />
+          </div>
+          
+          <div className="form-group">
+            <label>确认密码</label>
+            <input
+              type="password"
+              value={confirmPassword}
+              onChange={(e) => setConfirmPassword(e.target.value)}
+              required
+              placeholder="再次输入密码"
+            />
+          </div>
+          
+          <button type="submit" className="btn-primary" disabled={loading}>
+            {loading ? '注册中...' : '注册'}
+          </button>
+        </form>
+        
+        <p className="auth-tip">
+          已有账号？<a href="#login" onClick={(e) => { e.preventDefault(); onRegister(null, 'login'); }}>立即登录</a>
+        </p>
+      </div>
+    </div>
+  );
+}
+
+export default Register;

frontend-react/src/index.css

@@ -262,6 +262,128 @@ header p {
   color: #999;
 }
 
+/* 认证界面 */
+.auth-container {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  min-height: 100vh;
+  padding: 20px;
+}
+
+.auth-card {
+  background: white;
+  padding: 40px;
+  border-radius: 10px;
+  box-shadow: 0 4px 20px rgba(0,0,0,0.2);
+  width: 100%;
+  max-width: 400px;
+}
+
+.auth-card h1 {
+  color: #667eea;
+  font-size: 2em;
+  text-align: center;
+  margin-bottom: 10px;
+}
+
+.auth-card h2 {
+  color: #333;
+  font-size: 1.5em;
+  text-align: center;
+  margin-bottom: 30px;
+}
+
+.form-group {
+  margin-bottom: 20px;
+}
+
+.form-group label {
+  display: block;
+  color: #555;
+  font-weight: 500;
+  margin-bottom: 8px;
+}
+
+.form-group input {
+  width: 100%;
+  padding: 12px;
+  border: 1px solid #ddd;
+  border-radius: 5px;
+  font-size: 1em;
+  transition: border-color 0.2s;
+}
+
+.form-group input:focus {
+  outline: none;
+  border-color: #667eea;
+}
+
+.btn-primary {
+  width: 100%;
+  padding: 12px;
+  background: linear-gradient(135deg, #667eea, #764ba2);
+  color: white;
+  border: none;
+  border-radius: 5px;
+  font-size: 1.1em;
+  font-weight: 600;
+  cursor: pointer;
+  transition: transform 0.2s;
+}
+
+.btn-primary:hover {
+  transform: translateY(-2px);
+}
+
+.btn-primary:disabled {
+  opacity: 0.6;
+  cursor: not-allowed;
+}
+
+.auth-tip {
+  text-align: center;
+  margin-top: 20px;
+  color: #666;
+}
+
+.auth-tip a {
+  color: #667eea;
+  text-decoration: none;
+}
+
+.auth-tip a:hover {
+  text-decoration: underline;
+}
+
+/* 用户信息 */
+.header-content {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+}
+
+.user-info {
+  display: flex;
+  align-items: center;
+  gap: 15px;
+  color: white;
+}
+
+.btn-logout {
+  padding: 8px 16px;
+  background: rgba(255,255,255,0.2);
+  color: white;
+  border: 1px solid rgba(255,255,255,0.5);
+  border-radius: 5px;
+  cursor: pointer;
+  transition: background 0.2s;
+}
+
+.btn-logout:hover {
+  background: rgba(255,255,255,0.3);
+}
+
 /* 移动端 */
 @media (max-width: 768px) {
   .grid-2 {