feat: fpw plugins, validation/crawl perf, WS stats, test DB isolation

- Add Free_Proxy_Website-style fpw_* plugins and register them
- Per-plugin crawl timeout (crawl_timeout_seconds=120); remove global crawl_timeout setting
- Validator: fix connect vs total timeout on save; SOCKS session LRU cache; drop redundant semaphore
- Validation handler uses single DB connection; batch upsert after crawl; WorkerPool put_nowait
- Remove unused max_retries from settings API/UI; settings maintenance SQL + init_db cleanup of deprecated keys
- WebSocket dashboard stats; ProxyList pool_filter and API alignment
- POST /api/proxies/delete-one for IPv6-safe deletes; task poll stops on 404
- pytest uses PROXYPOOL_DB_PATH=db/proxies.test.sqlite so tests do not wipe production DB
- .gitignore: explicit proxies.test.sqlite patterns; fix plugin_service ValidationException import

Made-with: Cursor

pytest.ini

@@ -1,4 +1,4 @@
-[tool:pytest]
+[pytest]
 testpaths = tests
 python_files = test_*.py
 python_classes = Test*
@@ -13,5 +13,6 @@ markers =
     integration: 集成测试
     e2e: 端到端测试
     slow: 慢速测试
+    network: 需要出站网络（真实爬取/验证）
     async_test: 异步测试
 asyncio_default_fixture_loop_scope = function