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

tests/support/plugins_for_runner.py

@@ -0,0 +1,19 @@
+"""供 PluginRunner 等测试使用的真实插件子类（非 unittest.mock）。"""
+from typing import List
+
+from app.core.plugin_system.base import BaseCrawlerPlugin
+from app.models.domain import ProxyRaw
+
+
+class UnhealthyPlugin(BaseCrawlerPlugin):
+    """health_check 抛错，用于验证 Runner 对异常的统计与落库。"""
+
+    name = "test_unhealthy_runner"
+    display_name = "TestUnhealthy"
+    description = "PluginRunner health_check failure test double"
+
+    async def crawl(self) -> List[ProxyRaw]:
+        return []
+
+    async def health_check(self) -> bool:
+        raise RuntimeError("network down")