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

app/services/plugin_service.py

@@ -5,7 +5,7 @@ from typing import List, Optional
 from app.core.db import get_db
 from app.core.plugin_system.registry import registry
 from app.core.plugin_system.base import BaseCrawlerPlugin
-from app.core.exceptions import PluginNotFoundException
+from app.core.exceptions import PluginNotFoundException, ValidationException
 from app.repositories.settings_repo import PluginSettingsRepository
 from app.models.domain import PluginInfo, ProxyRaw, CrawlResult
 from app.core.log import logger