fix(chatbot): row_factory=dict_row در sync_chunks و fetch_all_chunks

بدون آن، psycopg3 تاپل برمی‌گرداند و row["model"] خطای
«tuple indices must be integers or slices, not str» می‌داد؛ نتیجه:
«Initial index sync failed» و unavailable ماندن چت با وجود امبد موفق.

chatbot/vectorstore.py

@@ -77,6 +77,7 @@ def sync_chunks(chunks: list[dict], force: bool = False) -> dict:
     خروجی: آمار عملیات برای لاگ.
     """
     import psycopg
+    from psycopg.rows import dict_row
     from psycopg.types.json import Jsonb
 
     from .embeddings import get_embeddings
@@ -84,7 +85,10 @@ def sync_chunks(chunks: list[dict], force: bool = False) -> dict:
     model = settings.embedding_model
     wanted = {c["doc_id"]: c for c in chunks}
 
-    with psycopg.connect(chatbot_dsn(), autocommit=True, connect_timeout=10) as conn:
+    # row_factory لازم است: پایین‌تر row["model"]/row["doc_id"] خوانده می‌شود و
+    # پیش‌فرض psycopg3 تاپل برمی‌گرداند (خطای tuple indices must be integers).
+    with psycopg.connect(chatbot_dsn(), autocommit=True, connect_timeout=10,
+                         row_factory=dict_row) as conn:
         existing: dict[str, str] = {}
         if not force:
             for row in conn.execute("SELECT doc_id, content_hash, model FROM chatbot_chunks").fetchall():
@@ -136,8 +140,10 @@ def sync_chunks(chunks: list[dict], force: bool = False) -> dict:
 def fetch_all_chunks() -> list[dict]:
     """همه قطعات ذخیره‌شده (برای ساخت BM25 در حافظه)."""
     import psycopg
+    from psycopg.rows import dict_row
 
-    with psycopg.connect(chatbot_dsn(), autocommit=True, connect_timeout=10) as conn:
+    with psycopg.connect(chatbot_dsn(), autocommit=True, connect_timeout=10,
+                         row_factory=dict_row) as conn:
         rows = conn.execute(
             "SELECT doc_id, content_hash, content FROM chatbot_chunks ORDER BY doc_id"
         ).fetchall()