refactor: derive VK description postfix from measure_name, drop global postfix setting

Each product's description is now built as "Name (цена за M.)" using its
own measure_name. The global description_postfix setting is removed —
it couldn't handle per-product units.

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

web/routes/sync.py

@@ -49,7 +49,6 @@ async def sync_settings_post(request: Request, db: Session = Depends(get_db)):
 
     form = await request.form()
     raw_multiplier = str(form.get("price_multiplier", "1")).strip()
-    postfix = str(form.get("description_postfix", "")).strip() or None
 
     try:
         multiplier = float(raw_multiplier)
@@ -61,13 +60,11 @@ async def sync_settings_post(request: Request, db: Session = Depends(get_db)):
     config = db.query(SyncConfig).filter_by(user_id=user.id).first()
     if config:
         config.price_multiplier = multiplier
-        config.description_postfix = postfix
     else:
         config = SyncConfig(
             user_id=user.id,
             is_enabled=False,
             price_multiplier=multiplier,
-            description_postfix=postfix,
         )
         db.add(config)