fix: resolve all ruff and ESLint lint errors
Backend (ruff):
- F821: Add TYPE_CHECKING imports for Vehicle, Contact, File in models
(file.py, retouch.py, sale.py, vehicle.py)
- E741: Rename ambiguous variable to /
(copilot_service.py, price_compare_service.py, openrouter.py)
- F841: Remove unused variable in sale_service.py
Frontend (ESLint):
- react/no-unescaped-entities: Escape quotes in ContractPreview.tsx
- @next/next/no-img-element: Replace <img> with <Image> from next/image
(FileGallery.tsx, FileList.tsx, FilePreview.tsx, BeforeAfterSlider.tsx)
Tests: 392 backend passed, 112 frontend passed, next build successful
Leopoldadmin
341d0c6f38