fix: 修复6个bug并接入CodeStable工作流

Bug修复:
- GetWorkList 使用了错误的 RecordType (RecordStudy→RecordWork)
- AllRecord handler 返回错误的分页信息 (page硬编码1, pageSize用RecordsCount)
- CourseParse creditNode nil panic (加nil检查)
- WebSocket CheckOrigin 安全漏洞 (release模式限制为同源)
- math/rand 可预测 (替换为 crypto/rand)
- GetDiscussList 未实现 (补全实现, 移除重复路由)

其他:
- 接入 CodeStable 工作流体系 (codestable/ 骨架 + AGENTS.md)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/router/router.go

@@ -73,7 +73,6 @@ func SetupRouter() *gin.Engine {
 			debug.GET("/logs", handler.DebugLogs)
 			debug.GET("/logs/download", handler.DebugLogsDownload)
 			debug.GET("/logs/ws", handler.DebugLogWS)
-			debug.GET("/ws/logs", handler.DebugLogWS)
 		}
 		v1 := api.Group("/v1")
 		{