Add configurable CC cost for banner vehicle PDF/description view

- Add cc_per_banner_view setting to system_settings (default 0.1 CC)
- Update car detail page to use dynamic CC value from settings
- Add CC per Banner View field in admin settings page
- Replace hardcoded 0.1 CC with configurable value

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/api/cc.py

@@ -146,7 +146,12 @@ def check_car_view(
     }
 
 
-PERFORMANCE_CHECK_COST = 0.1  # 0.1 CC for performance check view
+def get_performance_check_cost(db: Session) -> float:
+    """Get performance check cost from system settings"""
+    system_settings = db.query(SystemSettings).first()
+    if system_settings and system_settings.cc_per_banner_view is not None:
+        return system_settings.cc_per_banner_view
+    return 0.1  # Default fallback
 
 
 @router.post("/purchase-performance-check")
@@ -155,8 +160,9 @@ async def purchase_performance_check_view(
     current_user: User = Depends(get_current_user),
     db: Session = Depends(get_db)
 ):
-    """Purchase access to view performance check (costs 0.1 CC)"""
+    """Purchase access to view performance check (costs CC based on system settings)"""
     car_id = request.car_id
+    PERFORMANCE_CHECK_COST = get_performance_check_cost(db)
 
     # Check if car exists
     car = db.query(Car).filter(Car.id == car_id).first()