初始化知识库网页系统

功能：
- 用户登录/退出
- 文档列表展示（支持子目录）
- 关键词搜索
- Markdown 文档在线查看
- 管理员添加用户脚本

index.php

@@ -0,0 +1,64 @@
+<?php
+require_once 'config.php';
+
+// 已登录则跳转到主页
+if (isset($_SESSION['user_id'])) {
+    header('Location: dashboard.php');
+    exit;
+}
+
+$error = '';
+
+if ($_SERVER['REQUEST_METHOD'] === 'POST') {
+    $username = trim($_POST['username'] ?? '');
+    $password = $_POST['password'] ?? '';
+    
+    if (empty($username) || empty($password)) {
+        $error = '请输入用户名和密码';
+    } else {
+        $db = getDB();
+        $stmt = $db->prepare("SELECT * FROM users WHERE username = ?");
+        $stmt->execute([$username]);
+        $user = $stmt->fetch();
+        
+        if ($user && password_verify($password, $user['password_hash'])) {
+            $_SESSION['user_id'] = $user['id'];
+            $_SESSION['username'] = $user['username'];
+            header('Location: dashboard.php');
+            exit;
+        } else {
+            $error = '用户名或密码错误';
+        }
+    }
+}
+?>
+<!DOCTYPE html>
+<html lang="zh-CN">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>知识库 - 登录</title>
+    <link rel="stylesheet" href="style.css">
+</head>
+<body>
+    <div class="login-container">
+        <div class="login-box">
+            <h1>📚 知识库</h1>
+            <?php if ($error): ?>
+                <div class="error"><?php echo htmlspecialchars($error); ?></div>
+            <?php endif; ?>
+            <form method="POST" action="">
+                <div class="form-group">
+                    <label for="username">用户名</label>
+                    <input type="text" id="username" name="username" required autofocus>
+                </div>
+                <div class="form-group">
+                    <label for="password">密码</label>
+                    <input type="password" id="password" name="password" required>
+                </div>
+                <button type="submit" class="btn-primary">登录</button>
+            </form>
+        </div>
+    </div>
+</body>
+</html>