refactor(backup): remove built-in WuKongIM backup module (#139)

modules/backup/1module.go

@@ -1,9 +1,30 @@
+// Package backup is a tombstone for the removed built-in WuKongIM backup
+// module (issue #139). The Go code (cron scheduler, /v1/manager/backup/*
+// API, tar+COS storage, disk precheck — ~1.6k LoC) has been deleted; only
+// the two historical SQL migrations remain so sql-migrate continues to
+// recognise their IDs.
+//
+// Why a tombstone instead of deleting the SQL files outright:
+//   - Deleting them would leave orphaned IDs in gorp_migrations on existing
+//     deployments — sql-migrate's PlanMigration stage panics with "unknown
+//     migration in database" the moment it sees an ID with no embedded file.
+//   - Purging those rows at startup would let a rollback to a pre-removal
+//     release silently re-run the original CREATE TABLE statements (no
+//     IF NOT EXISTS) and fail at startup with MySQL 1050 because
+//     backup_config / backup_history are intentionally kept on disk.
+//
+// SetupAPI is intentionally nil — no HTTP surface is registered. Only the
+// SQLDir is exposed so the embedded migrations stay discoverable.
+//
+// The backup_config / backup_history tables themselves are deliberately
+// left in place (per issue #139's removal plan) so existing production
+// rows are not lost. A future change may add a drop migration once we are
+// confident no deployment depends on the data.
 package backup
 
 import (
 	"embed"
 
-	"github.com/Mininglamp-OSS/octo-lib/config"
 	"github.com/Mininglamp-OSS/octo-lib/pkg/register"
 )
 
@@ -13,10 +34,7 @@ var sqlFS embed.FS
 func init() {
 	register.AddModule(func(ctx interface{}) register.Module {
 		return register.Module{
-			Name: "backup",
-			SetupAPI: func() register.APIRouter {
-				return NewManager(ctx.(*config.Context))
-			},
+			Name:   "backup",
 			SQLDir: register.NewSQLFS(sqlFS),
 		}
 	})