filer: validate bucket names before the SQL DDL hooks (#12547)

* filer: validate bucket names before the SQL DDL hooks

The SQL store builds CREATE TABLE and DROP TABLE statements by formatting
the bucket name into the query. The DML paths already reject names that
fail VerifyS3BucketName, but the bucket-creation and bucket-deletion
hooks ran the DDL without that check, so a name reaching them through the
filer or WebDAV directory path (which skips the check for dot-prefixed
directories) could inject stacked statements. Apply the same validation
the DML paths use.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* filer: check that a valid bucket runs both DDL statements

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

weed/filer/abstract_sql/abstract_sql_store.go

@@ -50,6 +50,9 @@ func (store *AbstractSqlStore) CanDropWholeBucket() bool {
 	return store.SupportBucketTable && !store.SkipDDL
 }
 func (store *AbstractSqlStore) OnBucketCreation(bucket string) {
+	if !isValidBucket(bucket) {
+		return
+	}
 	store.dbsLock.Lock()
 	defer store.dbsLock.Unlock()
 
@@ -61,6 +64,9 @@ func (store *AbstractSqlStore) OnBucketCreation(bucket string) {
 	store.dbs[bucket] = true
 }
 func (store *AbstractSqlStore) OnBucketDeletion(bucket string) {
+	if !isValidBucket(bucket) {
+		return
+	}
 	store.dbsLock.Lock()
 	defer store.dbsLock.Unlock()