实现插件配置持久化与任务队列持久化

插件配置持久化：
- plugin_settings 表新增 config_json 字段，支持存储每个插件的自定义配置
- BaseCrawlerPlugin 新增 default_config 属性和 update_config 方法
- PluginSettingsRepository 新增 get_config / set_config 方法
- PluginService 新增 get_plugin_config 和 update_plugin_config
- api/routes/plugins.py 新增 GET /{id}/config 和 POST /{id}/config 接口
- 前端 Plugins.vue 增加配置编辑对话框，支持动态渲染数字/布尔/字符串类型配置
- ip3366 插件示例化：增加 max_pages 配置项，验证配置生效后会动态更新爬取 URL

任务队列持久化：
- 新建 validation_tasks 表：id, ip, port, protocol, status, result, response_time_ms, created_at, updated_at
- 新建 ValidationTaskRepository，提供 insert_batch / acquire_pending / complete_task / reset_processing 等方法
- ValidationQueue 重构：
  - submit() 时把任务写入数据库并唤醒 Worker
  - Worker 通过 acquire_pending 原子取任务并验证
  - 验证完成后更新任务状态并入库有效代理
  - 启动时自动恢复之前中断的 processing 任务为 pending
  - 支持 drain() 等待所有 pending 完成
- 调度器验证流程同样自动持久化到任务表

其他适配：
- 更新 api/deps.py 和 api/lifespan.py，移除对已删除 settings_service 的残留引用
- 更新前端 pluginService.js 和 api/index.js 增加配置相关 API

repositories/settings_repo.py

@@ -93,10 +93,48 @@ class PluginSettingsRepository:
             return False
 
     @staticmethod
-    async def list_all(db: aiosqlite.Connection) -> Dict[str, bool]:
+    async def get_config(db: aiosqlite.Connection, plugin_id: str) -> Optional[Dict[str, Any]]:
+        async with db.execute(
+            "SELECT config_json FROM plugin_settings WHERE plugin_id = ?", (plugin_id,)
+        ) as cursor:
+            row = await cursor.fetchone()
+            if row and row[0]:
+                try:
+                    return json.loads(row[0])
+                except json.JSONDecodeError:
+                    return None
+            return None
+
+    @staticmethod
+    async def set_config(db: aiosqlite.Connection, plugin_id: str, config: Dict[str, Any]) -> bool:
+        try:
+            await db.execute(
+                """
+                INSERT INTO plugin_settings (plugin_id, config_json, updated_at)
+                VALUES (?, ?, CURRENT_TIMESTAMP)
+                ON CONFLICT(plugin_id) DO UPDATE SET
+                    config_json = excluded.config_json,
+                    updated_at = CURRENT_TIMESTAMP
+                """,
+                (plugin_id, json.dumps(config, ensure_ascii=False)),
+            )
+            await db.commit()
+            return True
+        except Exception as e:
+            logger.error(f"set_config failed for {plugin_id}: {e}")
+            return False
+
+    @staticmethod
+    async def list_all(db: aiosqlite.Connection) -> Dict[str, Dict[str, Any]]:
         result = {}
-        async with db.execute("SELECT plugin_id, enabled FROM plugin_settings") as cursor:
+        async with db.execute("SELECT plugin_id, enabled, config_json FROM plugin_settings") as cursor:
             rows = await cursor.fetchall()
-            for plugin_id, enabled in rows:
-                result[plugin_id] = bool(enabled)
+            for plugin_id, enabled, config_json in rows:
+                config = {}
+                if config_json:
+                    try:
+                        config = json.loads(config_json)
+                    except json.JSONDecodeError:
+                        pass
+                result[plugin_id] = {"enabled": bool(enabled), "config": config}
         return result