enhanced questionnaire version handling and handling uploads from outdated questionnaires through automatic revisioning and checks

lib/read_db_cache.php

@@ -19,6 +19,8 @@ function qdb_read_db_open(): array {
     }
 
     [$pdo, $memfdPath, $memfdFd] = qdb_read_materialize_decrypted_db();
+    // Materialize may persist a migration (updates QDB_PATH mtime); refresh signature before caching.
+    $signature = qdb_read_cache_signature();
     qdb_read_cache_store($signature, $pdo, $memfdPath, $memfdFd);
     return [$pdo, QDB_READONLY_CACHE_HANDLE, null];
 }