Backfill default keys in DB get_sequence for API responses

Ensures the project loader API always returns all expected keys
like mode, cfg, etc. even if they were missing from stored data.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

db.py

@@ -5,7 +5,7 @@ import time
 from pathlib import Path
 from typing import Any
 
-from utils import load_json, KEY_BATCH_DATA, KEY_HISTORY_TREE
+from utils import load_json, DEFAULTS, KEY_BATCH_DATA, KEY_HISTORY_TREE
 
 logger = logging.getLogger(__name__)
 
@@ -231,7 +231,10 @@ class ProjectDB:
         ).fetchone()
         if not row:
             return None
-        return self._migrate_lora_keys(json.loads(row["data"]))
+        data = json.loads(row["data"])
+        for k, v in DEFAULTS.items():
+            data.setdefault(k, v)
+        return self._migrate_lora_keys(data)
 
     def list_sequences(self, data_file_id: int) -> list[int]:
         rows = self.conn.execute(