fix(chatbot): کوتیشن desc در سه کوئری دیگر ایندکس

همان باگ قبلی در investment_models/process_steps/why_us/timeline هم بود؛
بدون این، سینک ایندکس ناقص می‌ماند و بخشی از محتوا هرگز بردار نمی‌گرفت.

chatbot/content.py

@@ -166,7 +166,7 @@ def fetch_site_documents(database_url: str) -> list[dict]:
             docs.append(d)
 
     # --- مدل‌های سرمایه‌گذاری ---
-    for row in _fetch_rows(dsn, "SELECT title, desc, points FROM investment_models ORDER BY position"):
+    for row in _fetch_rows(dsn, 'SELECT title, "desc", points FROM investment_models ORDER BY position'):
         points = "؛ ".join(_clean(p) for p in (row["points"] or []))
         d = _doc(
             "\n".join(filter(None, [
@@ -179,7 +179,7 @@ def fetch_site_documents(database_url: str) -> list[dict]:
             docs.append(d)
 
     # --- مراحل همکاری ---
-    for row in _fetch_rows(dsn, "SELECT step, title, desc FROM process_steps ORDER BY position"):
+    for row in _fetch_rows(dsn, 'SELECT step, title, "desc" FROM process_steps ORDER BY position'):
         d = _doc(
             f"مرحله {_clean(row['step'])} — {_clean(row['title'])}: {_clean(row['desc'])}",
             "process", _clean(row["title"]), "/investment",
@@ -188,7 +188,7 @@ def fetch_site_documents(database_url: str) -> list[dict]:
             docs.append(d)
 
     # --- چرا ما / تیم / نظرسنجی / تایم‌لاین / داستان ما ---
-    for row in _fetch_rows(dsn, "SELECT title, desc FROM why_us ORDER BY position"):
+    for row in _fetch_rows(dsn, 'SELECT title, "desc" FROM why_us ORDER BY position'):
         d = _doc(f"{_clean(row['title'])}: {_clean(row['desc'])}", "about", _clean(row["title"]), "/about")
         if d:
             docs.append(d)
@@ -209,7 +209,7 @@ def fetch_site_documents(database_url: str) -> list[dict]:
         if d:
             docs.append(d)
 
-    for row in _fetch_rows(dsn, "SELECT year, title, desc FROM timeline ORDER BY position"):
+    for row in _fetch_rows(dsn, 'SELECT year, title, "desc" FROM timeline ORDER BY position'):
         d = _doc(
             f"سال {_clean(row['year'])} — {_clean(row['title'])}: {_clean(row['desc'])}",
             "timeline", _clean(row["title"]), "/about",