重构: 迁移后端代码到 app 目录，前端移动到 WebUI，添加完整测试套件

主要变更:
- 后端代码从根目录迁移到 app/ 目录
- 前端代码从 frontend/ 重命名为 WebUI/
- 更新所有导入路径以适配新结构
- 提取公共 API 响应函数到 app/api/common.py
- 精简验证器服务代码
- 更新启动脚本和文档

测试:
- 新增完整测试套件 (tests/)
- 单元测试: 模型、仓库层
- 集成测试: 覆盖所有 22+ API 端点
- E2E 测试: 4个完整工作流场景
- 添加 pytest 配置和测试运行脚本

app/services/validator_service.py

@@ -0,0 +1,97 @@
+"""代理验证服务 - 支持 HTTP/HTTPS/SOCKS4/SOCKS5"""
+import asyncio
+import random
+import time
+import aiohttp
+import aiohttp_socks
+from typing import Tuple
+from app.core.log import logger
+
+
+class ValidatorService:
+    """代理验证器"""
+
+    # 测试 URL
+    TEST_URLS = {
+        "http": ["http://httpbin.org/ip", "http://api.ipify.org"],
+        "https": ["https://httpbin.org/ip", "https://api.ipify.org"],
+    }
+
+    def __init__(
+        self,
+        timeout: float = 5.0,
+        connect_timeout: float = 3.0,
+        max_concurrency: int = 50,
+    ):
+        self.timeout = timeout
+        self.connect_timeout = connect_timeout
+        self.semaphore = asyncio.Semaphore(max_concurrency)
+
+    def _get_test_url(self, protocol: str) -> str:
+        """获取测试 URL"""
+        urls = self.TEST_URLS.get(protocol.lower(), self.TEST_URLS["http"])
+        return random.choice(urls)
+
+    async def validate(self, ip: str, port: int, protocol: str = "http") -> Tuple[bool, float]:
+        """验证单个代理，返回 (是否有效, 延迟毫秒)"""
+        protocol = protocol.lower()
+        
+        async with self.semaphore:
+            start = time.time()
+            try:
+                if protocol in ("socks4", "socks5"):
+                    return await self._validate_socks(ip, port, protocol, start)
+                else:
+                    return await self._validate_http(ip, port, protocol, start)
+            except asyncio.TimeoutError:
+                logger.debug(f"Validation timeout: {ip}:{port} ({protocol})")
+                return False, 0.0
+            except Exception as e:
+                logger.debug(f"Validation error {ip}:{port} ({protocol}): {e}")
+                return False, 0.0
+
+    async def _validate_http(self, ip: str, port: int, protocol: str, start: float) -> Tuple[bool, float]:
+        """验证 HTTP/HTTPS 代理"""
+        proxy_url = f"http://{ip}:{port}"
+        connector = aiohttp.TCPConnector(ssl=False, limit=0, force_close=True)
+        timeout = aiohttp.ClientTimeout(total=self.timeout, connect=self.connect_timeout)
+        test_url = self._get_test_url(protocol)
+
+        try:
+            async with aiohttp.ClientSession(connector=connector, timeout=timeout) as session:
+                async with session.get(test_url, proxy=proxy_url, allow_redirects=True) as response:
+                    if response.status in (200, 301, 302):
+                        latency = round((time.time() - start) * 1000, 2)
+                        logger.info(f"HTTP valid: {ip}:{port} ({protocol}) {latency}ms")
+                        return True, latency
+                    return False, 0.0
+        finally:
+            await connector.close()
+
+    async def _validate_socks(self, ip: str, port: int, protocol: str, start: float) -> Tuple[bool, float]:
+        """验证 SOCKS4/SOCKS5 代理"""
+        proxy_type = (
+            aiohttp_socks.ProxyType.SOCKS4
+            if protocol == "socks4"
+            else aiohttp_socks.ProxyType.SOCKS5
+        )
+        connector = aiohttp_socks.ProxyConnector(
+            proxy_type=proxy_type,
+            host=ip,
+            port=port,
+            rdns=True,
+            ssl=False,
+        )
+        timeout = aiohttp.ClientTimeout(total=self.timeout, connect=self.connect_timeout)
+        test_url = self._get_test_url("http")
+
+        try:
+            async with aiohttp.ClientSession(connector=connector, timeout=timeout) as session:
+                async with session.get(test_url, allow_redirects=True) as response:
+                    if response.status in (200, 301, 302):
+                        latency = round((time.time() - start) * 1000, 2)
+                        logger.info(f"SOCKS valid: {ip}:{port} ({protocol}) {latency}ms")
+                        return True, latency
+                    return False, 0.0
+        finally:
+            await connector.close()