refactor(crawl): parallel plugins via JobExecutor; per-plugin throttle

- Remove global crawl_slot gate; all CrawlJobs share only executor semaphore
- max_concurrent_jobs = max(24, n_plugins+8) for crawl-all + aggregator headroom
- BaseHTTPPlugin max_concurrency 3->2; fpw multi-URL plugins 4->2
- fetch_all: short random delay before each request to ease single-host pressure

Made-with: Cursor

app/plugins/base.py

@@ -26,7 +26,7 @@ class BaseHTTPPlugin(BaseCrawlerPlugin):
         self.urls: List[str] = []
         self.current_url: str = ""
         self._client: Optional[httpx.AsyncClient] = None
-        self.max_concurrency: int = 3
+        self.max_concurrency: int = 2
 
     def get_headers(self) -> dict:
         return {
@@ -178,6 +178,7 @@ class BaseHTTPPlugin(BaseCrawlerPlugin):
 
         async def _fetch_limited(url: str):
             async with semaphore:
+                await asyncio.sleep(random.uniform(0.08, 0.45))
                 return await self.fetch(url, timeout=timeout, retries=retries)
 
         tasks = [_fetch_limited(url) for url in urls]

app/plugins/fpw_proxy_list_download.py

@@ -13,7 +13,7 @@ class FpwProxyListDownloadPlugin(BaseHTTPPlugin):
 
     def __init__(self):
         super().__init__()
-        self.max_concurrency = 4
+        self.max_concurrency = 2
         self.api_pairs = [
             ("http", "https://www.proxy-list.download/api/v1/get?type=http"),
             ("https", "https://www.proxy-list.download/api/v1/get?type=https"),

app/plugins/fpw_socks_ssl_proxy.py

@@ -14,7 +14,7 @@ class FpwSocksSslProxyPlugin(BaseHTTPPlugin):
 
     def __init__(self):
         super().__init__()
-        self.max_concurrency = 4
+        self.max_concurrency = 2
         # 与 sslproxies 同模板的镜像站较多，socks-proxy 在部分网络下不稳定，多源提高成功率
         self.urls = [
             "https://www.sslproxies.org/",