refactor(backend): optimize database safety, validator performance, and scheduler concurrency

- Fix SQL injection risks in proxy_repo and task_repo
- Atomic acquire_pending with UPDATE ... RETURNING
- Reuse aiohttp ClientSession in ValidatorService
- Replace polling with asyncio.Event in SchedulerService
- Optimize ValidationQueue.drain with asyncio.Condition
- Concurrent plugin crawling with asyncio.gather
- Unify ProxyRaw model import path
- Fix test baseline and remove tracked __pycache__ files

app/plugins/ip89.py

@@ -7,6 +7,7 @@ from app.core.log import logger
 
 
 class Ip89Plugin(BaseHTTPPlugin):
+    default_config = {"max_pages": 5}
     name = "ip89"
     display_name = "89免费代理"
     description = "从 89ip.cn 爬取免费代理"
@@ -35,5 +36,5 @@ class Ip89Plugin(BaseHTTPPlugin):
                         results.append(ProxyRaw(ip, int(port), "http"))
 
         if results:
-            logger.info(f"{self.display_name} 解析完成，获得 {len(results)} 个潜在代理")
+            logger.info(f"{self.display_name} 解析完成，获取 {len(results)} 个潜在代理")
         return results