feat(maintenance): add policy executor and config provider

ConfigProvider, PolicyExecutor, DBStatsProvider, scheduler и safety; зависимость robfig/cron/v3.

Co-authored-by: Cursor <cursoragent@cursor.com>

go.mod

@@ -25,6 +25,7 @@ require (
 	github.com/prometheus/common v0.55.0 // indirect
 	github.com/prometheus/procfs v0.15.1 // indirect
 	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
+	github.com/robfig/cron/v3 v3.0.1 // indirect
 	golang.org/x/crypto v0.46.0 // indirect
 	golang.org/x/mod v0.31.0 // indirect
 	golang.org/x/net v0.48.0 // indirect