feat(security): 添加 JWT 认证功能

- 在后端添加 JWT 认证过滤器 JwtAuthenticationTokenFilter
- 创建 JwtTokenUtil 工具类用于生成和验证 JWT token
- 在 application.yml 中配置 JWT 相关参数
- 更新前端 HomePage 组件，增加用户认证相关逻辑

biji-houdaun/src/main/java/com/test/bijihoudaun/util/JwtTokenUtil.java

@@ -0,0 +1,68 @@
+package com.test.bijihoudaun.util;
+
+import io.jsonwebtoken.Claims;
+import io.jsonwebtoken.Jwts;
+import io.jsonwebtoken.SignatureAlgorithm;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.security.core.userdetails.UserDetails;
+import org.springframework.stereotype.Component;
+
+import java.util.Date;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.function.Function;
+
+@Component
+public class JwtTokenUtil {
+
+    @Value("${jwt.secret}")
+    private String secret;
+
+    @Value("${jwt.expiration}")
+    private Long expiration;
+
+    // 从token中获取用户名
+    public String getUsernameFromToken(String token) {
+        return getClaimFromToken(token, Claims::getSubject);
+    }
+
+    // 从token中获取过期时间
+    public Date getExpirationDateFromToken(String token) {
+        return getClaimFromToken(token, Claims::getExpiration);
+    }
+
+    public <T> T getClaimFromToken(String token, Function<Claims, T> claimsResolver) {
+        final Claims claims = getAllClaimsFromToken(token);
+        return claimsResolver.apply(claims);
+    }
+
+    // 为了从token中获取任何信息，我们都需要密钥
+    private Claims getAllClaimsFromToken(String token) {
+        return Jwts.parser().setSigningKey(secret).parseClaimsJws(token).getBody();
+    }
+
+    // 检查token是否过期
+    private Boolean isTokenExpired(String token) {
+        final Date expiration = getExpirationDateFromToken(token);
+        return expiration.before(new Date());
+    }
+
+    // 为用户生成token
+    public String generateToken(UserDetails userDetails) {
+        Map<String, Object> claims = new HashMap<>();
+        return doGenerateToken(claims, userDetails.getUsername());
+    }
+
+    // 创建token
+    private String doGenerateToken(Map<String, Object> claims, String subject) {
+        return Jwts.builder().setClaims(claims).setSubject(subject).setIssuedAt(new Date(System.currentTimeMillis()))
+                .setExpiration(new Date(System.currentTimeMillis() + expiration * 1000))
+                .signWith(SignatureAlgorithm.HS512, secret).compact();
+    }
+
+    // 验证token
+    public Boolean validateToken(String token, UserDetails userDetails) {
+        final String username = getUsernameFromToken(token);
+        return (username.equals(userDetails.getUsername()) && !isTokenExpired(token));
+    }
+}