fix: 修复任务生命周期与调度就绪，优化执行和构建开销 (#3069)

* fix: harden task lifecycle and scheduler readiness

* fix: confine log writes to the configured log directory

* fix: verify complete build artifacts and untracked inputs

* fix: reconcile scheduler state and make stop win startup races

* fix: isolate cron generations and serialize scheduler recovery

back/protos/cron.proto

@@ -17,7 +17,10 @@ message ICron {
   string name = 5;
 }
 
-message AddCronRequest { repeated ICron crons = 1; }
+message AddCronRequest {
+  repeated ICron crons = 1;
+  bool replace = 2;
+}
 
 message AddCronResponse {}