fix(e2e): add spam store to Stalwart sidecar config

Stalwart 0.15.5 requires [storage].spam to be declared or it aborts
at startup with "Store not configured → Failed to migrate database".

Author: antono

e2e/harness/stalwart.ts

@@ -71,6 +71,7 @@ function buildConfig(opts: {
 		'fts = "rocksdb"',
 		'blob = "rocksdb"',
 		'lookup = "rocksdb"',
+		'spam = "rocksdb"',
 		'directory = "internal"',
 		'',
 		'[store.rocksdb]',