feat: add 7 built-in middleware components inspired by Hono.js

New Middleware:
- CORS: Cross-Origin Resource Sharing with full configuration support
- Cookie Helper: Cookie management with signed cookie support (HMAC-SHA256)
- JWT: JSON Web Token authentication (HS256/384/512)
- Bearer Auth: Simple Bearer token authentication
- Compression: Gzip and deflate response compression
- Rate Limiting: Request rate limiting with customizable stores
- Validator: Schema-based request validation

Features:
- Context store for middleware data sharing (get/set/get_client_ip)
- Middleware export module with utility functions
- Comprehensive property-based tests for all middleware
- Example file demonstrating all middleware usage

Files Added:
- cors.v, cookie.v, jwt.v, bearer_auth.v, compress.v, rate_limit.v, validator.v
- middleware.v (unified exports)
- examples/middleware_demo.v
- tests/test_*.v (9 new test files)

Documentation:
- Updated README.md with detailed middleware usage guide
- Added Schema Builder API documentation

bearer_auth.v

@@ -0,0 +1,137 @@
+module hono
+
+import net.http
+
+// BearerToken 类型 - 支持单 token 或多 token 配置
+pub type BearerToken = string | []string
+
+// BearerAuthOptions 结构体 - Bearer Auth 配置选项
+pub struct BearerAuthOptions {
+pub:
+	token         BearerToken                         // Token 配置（必需）
+	realm         string                              // WWW-Authenticate realm
+	prefix        string       = 'Bearer'             // 认证前缀，默认 "Bearer"
+	header_name   string       = 'Authorization'      // 请求头名称，默认 "Authorization"
+	hash_function ?fn (string) string                 // 哈希函数（用于安全比较）
+	verify_token  ?fn (string, Context) bool          // 自定义验证回调
+}
+
+// bearer_auth - Bearer Auth 中间件工厂函数
+// 返回一个 ContextMiddleware，用于验证 Bearer Token
+pub fn bearer_auth(options BearerAuthOptions) ContextMiddleware {
+	return fn [options] (mut c Context, next fn (mut Context) http.Response) http.Response {
+		// 获取 Authorization 头
+		auth_header := c.req.header.get_custom(options.header_name) or {
+			return unauthorized_response(mut c, options.realm, 'Missing authorization header')
+		}
+
+		if auth_header.len == 0 {
+			return unauthorized_response(mut c, options.realm, 'Missing authorization header')
+		}
+
+		// 解析 token
+		token := extract_bearer_token(auth_header, options.prefix) or {
+			return unauthorized_response(mut c, options.realm, 'Invalid token format')
+		}
+
+		// 验证 token
+		if !validate_bearer_token(token, options, c) {
+			return unauthorized_response(mut c, options.realm, 'Invalid token')
+		}
+
+		// 将 token 存储到 Context（便于后续使用）
+		c.set('bearer_token', token)
+
+		// 继续处理请求
+		return next(mut c)
+	}
+}
+
+// extract_bearer_token - 从 Authorization 头提取 token
+fn extract_bearer_token(auth_header string, prefix string) !string {
+	expected_prefix := '${prefix} '
+
+	if !auth_header.starts_with(expected_prefix) {
+		return error('Invalid authorization format')
+	}
+
+	token := auth_header[expected_prefix.len..].trim_space()
+
+	if token.len == 0 {
+		return error('Empty token')
+	}
+
+	return token
+}
+
+// validate_bearer_token - 验证 Bearer Token
+fn validate_bearer_token(token string, options BearerAuthOptions, c Context) bool {
+	// 优先使用自定义验证回调
+	if verify_fn := options.verify_token {
+		return verify_fn(token, c)
+	}
+
+	// 使用配置的 token 进行验证
+	match options.token {
+		string {
+			// 单 token 验证
+			return secure_token_compare(token, options.token, options.hash_function)
+		}
+		[]string {
+			// 多 token 验证
+			for valid_token in options.token {
+				if secure_token_compare(token, valid_token, options.hash_function) {
+					return true
+				}
+			}
+			return false
+		}
+	}
+}
+
+// secure_token_compare - 安全的 token 比较（防止时序攻击）
+fn secure_token_compare(provided string, expected string, hash_fn ?fn (string) string) bool {
+	// 如果提供了哈希函数，先对 token 进行哈希
+	if hash_function := hash_fn {
+		hashed_provided := hash_function(provided)
+		hashed_expected := hash_function(expected)
+		return constant_time_compare_bearer(hashed_provided, hashed_expected)
+	}
+
+	// 直接使用常量时间比较
+	return constant_time_compare_bearer(provided, expected)
+}
+
+// constant_time_compare_bearer - 常量时间字符串比较，防止时序攻击
+fn constant_time_compare_bearer(a string, b string) bool {
+	if a.len != b.len {
+		return false
+	}
+
+	mut result := u8(0)
+	for i := 0; i < a.len; i++ {
+		result |= a[i] ^ b[i]
+	}
+
+	return result == 0
+}
+
+// unauthorized_response - 返回 401 未授权响应
+fn unauthorized_response(mut c Context, realm string, message string) http.Response {
+	c.status(401)
+
+	// 设置 WWW-Authenticate 头
+	mut www_auth := 'Bearer'
+	if realm.len > 0 {
+		www_auth = 'Bearer realm="${realm}"'
+	}
+	c.headers['WWW-Authenticate'] = www_auth
+
+	return c.json('{"error":"Unauthorized","message":"${message}"}')
+}
+
+// get_bearer_token - 从 Context 获取已验证的 Bearer Token
+// 这是一个便捷方法，用于在 handler 中获取已验证的 token
+pub fn get_bearer_token(c Context) ?string {
+	return c.get('bearer_token')
+}